Drug-induced alterations of steroid hormone metabolism in man

The effects of phenobarbitone on urinary 6 beta-hydroxycortisol excretion and hepatic enzyme activity in the guinea-pig

Urinary 6 beta-hydroxycortisol is a useful, non-invasive index of microsomal mixed-function oxidase activity in man (review: [1]). Administration of phenobarbitone (40 mg/kg/day) for 4 days to male guinea-pigs, produced significant increases in hepatic microsomal cytochrome P-450 content and cytochrome P-450 reductase activity but did not increase 6 beta-hydroxycortisol excretion. The lack of relationship between urinary 5 beta-OHC excretion and microsomal mixed-function oxidase activity in the guinea-pig may be accounted for by the finding that 6 beta-hydroxycortisol itself undergoes extensive and variable metabolism in the guinea-pig.

The role of cytochrome P-450 in the synthesis of polar metabolites of aldosterone by microsomes of male rat liver

Among the tissues of the male rat studied, the largest quantities of the neutral polar metabolites of aldosterone were synthesized by the hepatic microsomal fraction. The polar metabolites of aldosterone were separated by HPLC into six peaks. Three peaks of non-polar (reduced) metabolites were also synthesized. Synthesis of at least four of the neutral polar metabolites was induced by phenobarbital and inhibited by both CO and SKF-525A. The rates of synthesis of these metabolites, which were linear up to 5 minutes, correlated well with the concentration of cytochrome P-450 in the liver microsomes. Addition of aldosterone to the microsomal fraction caused a pronounced type I change in the cytochrome P-450 spectrum. The half maximal spectral change (KS) for aldosterone was calculated to be 8 microM. These experiments indicate that the neutral polar metabolites of aldosterone are produced by cytochrome P-450 dependent hydroxy lations.

Enzymic modification of environmental intoxicants: the role of cytochrome P-450

As of November 1977, the American Chemical Society's Chemical Abstracts Service computer registry of chemicals contained 4039907 distinct entities, and has been growing at an average rate of about 6000 per week. How many of these chemicals are in everyday use? Current estimates from the Environmental Protection Agency indicate that there may be as many as 50000 commonly used chemicals, not including pesticides, pharmaceuticals, and food additives. The EPA estimates that there may be as many as 1500 different active ingredients in pesticides. The Food and Drug Administration estimates that there are about 4000 active ingredients in drugs and about 2000 other ancillary compounds used in the drug industry. The FDA also estimates that there are about 2500 additives used for nutritional value and flavouring and 3000 chemicals used to preserve processed food. Thus there seem to be about 63000 chemicals in common use.

o,p'-DDD (mitotane) therapy of adrenal cortical carcinoma: observations on drug dosage, toxicity, and steroid replacement

Four patients with adrenal cortical carcinoma were treated with standard doses of o,p'-DDD. Plasma levels of o,p'-DDD and its metabolites o,p'-DDA and o,p'-DDE were measured. o,p'-DDD was measurable for up to 8 months after stopping therapy, and trace levels of metabolites were detectable at 18 months. Although 2 of 3 patients with measurable disease had objective tumor response and one patient achieved a complete response, severe drug toxicity occurred in all patients and signs of adrenal insufficiency occurred in three. Low dose therapy with o,p'-DDD is suggested, together with full gluco and mineralocorticoid replacement. Measurement of o,p'-DDD and its metabolites in plasma may prove clinically useful in developing effective but less toxic dosage schedules.

Endocrine effects of alcohol

A variety of effects of alcohol on endocrine function are now well documented. Clinically, the most important of these are alcohol-induced 'pseudo-Cushing's syndrome' and a syndrome of hypothalamic-pituitary-adrenocortical unresponsiveness, both of which result from long-term over-indulgence, and impairment of testosterone secretion which may occur following relatively short-term drinking. Evidence indicates that a number of different mechanisms are responsible for mediating the effects of alcohol on endocrine function. In a few instances (e.g. inhibition of vasopressin secretion and impairment of steroidogenesis resulting in a fall in testosterone production rate), alcohol appears to influence directly the release or synthesis of individual hormones. However, the majority of the endocrine effects of alcohol are probably indirect, resulting from either the stress of intoxication (stimulation of cortisol, catecholamines and possibly GH and prolactin), changes in the level of intermediary metabolites (e.g. a fall in circulating FFA stimulating GH secretion) or changes in the metabolism of hormones (e.g. catecholamines, oestrogens, androgens) resulting from alteration in intracellular redox state or tissue damage.

Male pseudohermaphroditism due to steroid 5-alpha-reductase deficiency

A new inherited form of male pseudohermaphroditism has been investigated in a pedigree of 24 families with 38 affected males. At birth, the affected males (46 XY) have a clitoral-like phallus, bifid scrotum and urogenital sinus. The testes are in the inguinal canals or labial-scrotal folds. The Wolffian structures are normally differentiated; there are no Mullerian structures. At puberty a muscular male habitus develops with growth of the phallus and scrotum, voice change and no gynecomastia. The subjects have erections, ejaculations and a libido directed towards females. They have decreased body hair, a scant to absent beard, no temporal hair line recession and a small prostate. Testicular biopsy reveals a normal testis. The mean plasma T levels in affected adults are significantly higher, and the mean plasma DHT levels are significantly lower when compared to those in normal subjects. The plasma T:DHT ratios range from 35 to 84 compared to 8 to 16 in normal subjects. After the administration of hCG, the T:DHT ratios in affected male children range from 74 to 162 compared to 3 to 26 in the control subjects. In affected adults, mean plasma LH and FSH levels are significantly higher than in normal subjects. In the affected subjects, the metabolic clearance rates of T and DHT are normal, but the conversion ratio of T to DHT is less than 1 per cent. The endogenous mean urinary E:A and E-OH:A-OH ratios, and the urinary E:A and E-OH:A-OH ratios after the infusion of radioactive T are significantly higher than in normal males. Inheritance is autosomal recessive with some sibling sisters showing the same biochemical defect, and obligate carrier parents showing an intermediate defect. These data support our thesis that the defect in these male pseudohermaphrodites is secondary to decreased steroid delta 4-5 alpha-reductase activity. The affected subjects provide a clinical model for delineating the roles of T and DHT in sexual differentiation and development. This entity also demonstrates an inherited disorder of steroid metabolism in which the basic enzyme deficiency resides in the target tissues.

Studies in porphyria. II. Evidence for a deficiency of steroid delta-4-5-alpha-reductase activity in acute intermittent porphyria

Patients with the genetic liver disease, acute intermittent porphyria (AIP), have a defect in the reductive transformation of steroid hormones that is manifest by the disproportionate generation of 5beta-steroid metabolites from precursor hormones. 5beta-steroid metabolites were earlier shown to be potent inducers experimentally of delta-aminolevulinate synthetase (ALAS), the mitochondrial enzyme that is rate-limiting in porphyrin synthesis, and that is found at high levels of activity in the livers of AIP patients. In this report, the basis for the defective steroid metabolism in AIP has been shown, through studies with the (14)C-labeled adrenal hormone 11beta-hydroxy-Delta(4)-androstenedione, to reside in a substantial deficiency of hepatic steroid Delta(4)-5alpha-reductase activity. This enzymic deficiency was found in all seven AIP patients studied, and ranged from 34% to as much as 70% below the mean enzyme activity characterizing normal subjects. The functional consequence of the low levels of 5alpha-reductase activity in AIP is to divert the reductive transformation of certain natural hormones from the 5alpha- to the 5beta-pathway; the latter is the metabolic route through which endogenous steroids having the potential for inducing hepatic ALAS are generated. It is not presently known whether the 5alpha-reductase deficiency in AIP is acquired in some fashion or whether it has partial genetic determinants. It seems probable, however, that this enzymatic abnormality, coupled with the dramatic increase in hormone synthesis that occurs at puberty, may be of major importance in determining clinical expression of the latent gene defect for AIP in many individuals. The 5alpha-reductases for steroid hormones are known to be localized in the endoplasmic reticulum of hepatic cells and the present findings in AIP thus represent the first demonstration that an enzymic component of these membranous structures is functionally abnormal in this hereditary liver disease.