Pathologic Effects of Steroids: Some of the artificial steroids have greater pathogenic potency than do naturally occurring hormones. Desoxycorti-costerone, 2 α-methyl-9α-chlorocortisol, and other sodium-retaining steroids are damaging, especially if given to an animal (usually the rat) whose renal system is crippled by uninephrectomy and which is receiving an abnormally high load of sodium chloride. These animals may develop severe hypertension and sclerosis of vessels in the heart and kidney. Large doses of these steroids can cause some hypertension and some pathology when given for several weeks to normal rats on a commercial diet which contains approximately 1 per cent salt. If the sodium intake is reduced to the smallest amount of salt needed by the animal, hypertension and renal-cardiovascular pathology no longer occur.

Cortisone, hydrocortisone, corticosterone and whole adrenal cortical extract are each pathogenic when given in large doses to uninephrectomized salt-loaded rats. A point can be added here which can be used to support the Selye concept. In studies on adrenalectomized rats we have determined the amount of adrenal cortical extract needed to normalize resistance to severe stress. The most demanding stress in our experience is the Ingle muscle-work test in which the adrenalectomized rat requires 15 to 20 cc. of beef adrenal cortical extract per day in order to work normally.4 This suggests but does not prove that the adrenal cortices of the intact rat must secrete the activity equivalent of this amount of exogenous adrenal extract under the same conditions of stress. When 8 to 12 cc. per day of the same adrenal cortical extract is administered to uninephrectomized salt-loaded rats under nonstress conditions, hypertension with renal-cardiovascular damage results. Would not the same effects be caused by the secretion of comparable amounts of cortical hormones during severe stress? Perhaps not. Here we must search for differences in the effects of equivalent amounts of steroid during severe stress, when a high intake of steroid is needed to maintain life and optimal resistance, and under resting conditions, when the need for steroid is minimal. There is evidence in abundance that the amounts needed to sustain eucorticalism during severe stress will produce a state of hypercorticalism under resting conditions.

There are scant data on stressed and nonstressed animals with respect to the pathogenic effects of the same high intake of exogenous cortical hormone. The experimenter who would do a study of this sort on adrenalectomized and nonadrenalectomized animals, carefully exploring the dose-response effects of cortical hormone and the load-response effect of salt, all in the presence and absence of stress, should be rewarded by new insights into this problem.

Selye5 has described cardiac necroses in experimental animals treated with an excess of Na2HPO4 or NaClO4 in addition to overdosage with a sodium-retaining steroid. Myocardial damage will occur in 100 per cent of such animals stressed by neuromuscular exertion. There are no reports of stressors causing similar myocardial damage under naturally occurring conditions. Wilgram and Ingle" studied the effect of neuromuscular exertion alone on discarded breeder female rats without any increase in the incidence or severity of renal-cardiovascular lesions in these animals, which have some "spontaneous" damage in the hearts, vascular tree and kidneys.

There have been some studies on the effects of severe stress in the uninephrectomized, salt-loaded rat, but in relation to the amount that has been said and published on the importance of stress in causing disease, few data have been published.

ACTH: Wexler and Miller7 claim that small doses of long-acting ACTH cause an increase in the incidence and severity of renal-cardiovascular lesions which occur "spontaneously" in discarded breeder female rats from the Sprague-Dawley farms. This announcement that mild stimulation of the adrenal cortices is pathogenic created an understandable amount of excitement among laboratory and clinical investigators, for intact animals on a common laboratory diet were used in these studies. Wilgram and Ingle6 have given small, moderate and large doses of ACTH to similar rats with negative results. The reasons for these differences in results so dramatically positive in one report, so clearly negative in our own are not known.

Adrenal Enucleation: In the rat the adrenal can easily be enucleated by clipping off the distal tip of the gland and popping the remaining cortex from its capsule by gentle pressure on the sides of the gland. A layer of glomerulosa cells remains attached to the capsule, and cortical tissue regenerates from this remnant. When adrenal enucleation is done in the uninephrectomized rat given a high salt load (either 1 per cent saline to drink or 4 per cent salt diet), the animal develops hypertension and renal-cardiovascular disease after three or four weeks of adrenal regeneration. Although an abnormally high salt load and unilateral nephrectomy are both necessary conditions, we have here a kind of hypertensive vascular disease which seems referable to the adrenal cortex itself. The following hypothesis seemed plausible. Since the remaining glomerulosa cells secrete aldosterone a powerful sodium-retaining hormone, it was supposed that an excess of aldosterone and a subnormal amount of glucocorticoids are secreted during the regeneration of the enucleated adrenal gland. Direct studies of the secretory products of the regenerating cortex have failed to show either an excess of aldosterone or an abnormal secretory pattern of steroids. It has been postulated that, during the phase of cortical insufficiency which follows adrenal enucleation, the vascular tree becomes abnormally sensitive to steroids so that when secretion is renewed in the regenerating gland, the subnormal amount of steroids secreted now behaves like an excess. This is not the only interpretation that can be made of these puzzling results. We have supposed that the intact adrenal gland of the salt-loaded animal can suppress its secretion of sodium-retaining steroids to a minimum although not to zero. The salt-loaded animal having enucleated adrenals may be less able to suppress the secretion of sodium-retaining steroids during the phase of adrenal cortical regeneration. A comparison of the secretory products of normal and regenerating adrenal glands should be made under conditions of both minimal and high salt intake.

Whatever be the cause of adrenal regeneration hypertension, it seems possible that it is due to the trouble that the animal has in excreting salt- a high salt load and crippling of the excretory capacity by uninephrectomy are necessary conditions.

Stressors: When uninephrectomized salt-loaded rats are exposed to cold for several weeks, they develop nephrosclerosis and hypertensive vascular disease. Some animals develop cerebral hemorrhages-a dramatic and impressive event to bring about in laboratory animals by experiment. These changes are associated with a voluntary increase in the intake of the high salt diet. These cold-exposed animals must have more calories or they will die. When the intake of diet is restricted to that normally eaten at room temperature and the animal is allowed to drink a solution of sucrose to meet its increased need for energy, there is only a small amount of damage to the renal-cardiovascular systems. When uninephrectomized rats are tube-fed amounts of the high salt diet comparable to those eaten ad libitum by cold-exposed rats, the extent of damage at room temperature is almost as great as that occurring in the cold-exposed rats.

No other stressor has been shown to cause nephrosclerosis and hypertensive vascular disease in the uninephrectomized salt-loaded animal8 or in the normal animal. There is a small rise in blood pressure and some increase in inflammatory changes in kidneys and hearts of uninephrectomized salt-loaded rats subjected to laparotomy once per week, or a burn once per week or limb ligation shock once per week for eight weeks. Wilgram and Ingle6 have exposed aging rats to severe neuromuscular stress twice each week for eight weeks. These unoperated animals were maintained on a commercial diet without added salt. Some of these animals have spontaneously occurring hypertension, renal-cardiovascular diseases and other inflammatory and degenerative lesions. The incidence and severity of the damage were not increased above that of control animals of similar age.

Either a disciple or a critic of the Selye concept of adaptation diseases might easily imagine that the experimental production of diseases by nonspecific stressors under naturally occurring conditions would be a needed, even necessary, pillar of support, but the pillar is not there. Perhaps it will still be erected, for the possibility of getting positive evidence of this sort has not been exhausted.

Salt-loading: I have already hinted that salt (NaCl) may be the principal villain causing pathologic changes in the classic experiments of Professor Selye. Indeed, little or no guide should be needed toward this hypothesis. It would require some effort to avoid coming to grips with the idea. The importance of salt was appreciated by Professor Selye from the beginning of his studies, for he introduced the high salt load as a part of the causal pattern. However, he has characterized salt as a conditioning factor and has stated that salt-loading alone will not lead to renal-cardiovascular lesions with hypertension. It is true that experimental animals will not voluntarily drink enough 1 per cent saline (as used in most of Selye's experiments) to cause damage even in uninephrectomized animals unless some other factor such as a steroid is given to interfere with the renal excretion of sodium.

We have confirmed Meneely9 by showing that high dietary loads of sodium chloride can cause severe hypertension and renal-cardiovascular damage in uninephrectomized rats and somewhat milder changes in intact rats. The pathologic changes found at the end of an experimental period of two months is much less severe in the untreated adrenalectomized salt-loaded rat than in similar rats either having the adrenal glands intact or adrenalectomized and given adrenal cortex extract. The amelioration of damage is not complete. Adrenally insufficient rats show some positive correlation between salt-load and blood pressure, but it remains to be proven that full-blown hypertensive vascular disease can be caused by salt-loading in the absence of adrenal cortical hormones. Longer periods of salt-loading must be tested.

Now, when we have built some support for the proposition that salt is the primary cause of damage in the classical experiments of Selye, we stumble over the fact that adrenal cortical insufficiency will ameliorate the hypertension and the accompanying renal-cardiovascular diseases induced by salt-loading. We cannot escape the fact that the hormones of the adrenal cortex have some intimate connection with these disease processes. By what means does adrenal cortical insufficiency protect against the pathogenic effects of salt-loading? It seems improbable that salt-loading causes an increase in the secretion of adrenal steroids. Most of the available evidence indicates that a high salt load causes a significant decrease in the secretion of aldosterone, the most potent known sodium-retaining compound among the natural steroids. But salt-loading does not suppress the secretion of sodium-retaining steroids to zero and the basal secretion of the adrenal cortices may have some obligatory sodium-retaining action. The untreated adrenalectomized rat drinks less water than does the nonadrenalectomized rat given a dietary load of salt. We suppose that the animal without steroid can rid itself of sodium chloride more easily than can an animal in a state of eucorticalism, and that for this reason the pathogenic effects of a salt load are less. This is a hypothesis, not a known fact.

The salt-loaded, uninephrectomized, adrenalectomized rat is very sensitive to the administration of adrenal cortical extract.10 Doses of ACE which are too small to normalize all the metabolic aberrations of adrenal cortical insufficiency cause hypertension in rats fed a diet of 4 per cent salt. Here, again, we suppose that the intact adrenal glands can suppress the secretion of sodium-retaining steroids to a significant extent, but the rat given a uniform, although small, amount of ACE has fixed excess of exogenous sodium-retaining hormone coexisting with a deficiency of glucocorticoids. It is possible to cause nephrosclerosis and cardiovascular damage by giving doses of ACE much smaller than are required to maintain optimal resistance of adrenalectomized rats to severe stress.4