Sex difference in the activities of microsomal drug-metabolizing enzyme systems in relation to dietary protein

Sex Variation and Drug Therapy

A literature review of gender differences with drug therapy is presented.

Physiological differences between the sexes in basal metabolic rate and in levels of certain of the circulating hormones and enzymes affect or influence the metabolism of various drugs. Differences in muscle mass, disposition of adipose tissue and vascular resistance can lead to variations in response between the sexes to IM injections, while plasma levels of orally administered drugs can be influenced by sex differences such as gastric motility and secretion, metabolic rate, pregnancy, and differences in drug distributive compartments. These differences in gender response to a given therapy can vary according to the patient's age. Adverse reactions to drugs are also affected by the patient's gender, and certain drugs have been shown to induce adverse reactions predominantly in one sex.

The review illustrates the confusion surrounding this subject and stresses the importance of sex differences in the consideration and monitoring of drug therapy. Information on sex and age of patients, and possible sex differences in response to drug therapy is requested of all future therapeutic studies.

It was further suggested that the dual genetic coverage may be the mechanism by which the sex difference in susceptibility to infection can be explained. Support for this theory can best be found in a brief discussion of sex-linked diseases. The transmission from parents to offspring of defects, which may manifest themselves as disease, may be genetic in origin (Table 2).41

Due to the transmission of these diseases by the sex chromosomes, the male, having only one X-chromosome, is afflicted more often by these diseases. This leads one to conclude that given like conditions, females are better adapted to cope with many human diseases because they are genetically and chemically better evolved.

Effect of high-fat and high-protein diets on toxicity of parathion and dichlorvos

Growing male rats that weighed 120 +/- 5 g were kept for 30 days on the following synthetic diets: high protein diet (HPD), 59% casein; high fat diet (HFD), 50% saturated fat; and normal diet (ND), 19% casein, 10% saturated fat, and 60% sucrose. Other essential dietary ingredients were included in all the diets. All animals were injected at the end of the 30-day period with parathion [10 mg/kg intraperitoneal (ip) injection as a single dose] or dichlorvos (30 mg/kg ip as a single dose) to compare the effect of dietary pretreatments on mortality from parathion and dichlorvos. A lower dose of parathion (7.5 mg/kg) and dichlorvos (20 mg/kg) was employed in another set of experiments to compare the spontaneous regeneration of plasma and red blood cell (RBC) cholinesterase (ChE) activity at 2 hr, 1 day, 3 days, and 5 days after administration of parathion or dichlorvos. The effect of these diets on hepatic microsomal oxidases was also determined. Results showed that diets per se did not affect initial plasma and RBC ChE activity. The HPD and HFD significantly protected against mortality from parathion but not from dichlorvos. Hepatic microsomal cytochrome P-450 and aminopyrine demethylase activity were unchanged, but aniline hydroxylase activity was increased significantly by HPD and HFD. Parathion oxidase in hepatic microsomes was significantly increased in rats fed HFD only. For the HPD, spontaneous regeneration of ChE diminished in RBCs in parathion-intoxicated rats and in plasma and RBCs of dichlorvos-intoxicated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug metabolism under pathological and abnormal physiological states in animals and man

The activity of microsomal drug-metabolizing enzymes is altered by several pathological or abnormal physiological states, such as changes in nutritional status, liver, heart or kidney diseases, hormonal disturbances, pregnancy, tumour-bearing state, adjuvant arthritis, changes in reticuloendothelial system and environmental factors (stress, irradiation, heavy metals). The activities of other metabolic pathways, such as glucuronidation, sulphate conjugation, acetylation and alcohol oxidation are generally affected to lesser extents. Rats are most commonly used in drug metabolism studies, and it is important to know that the activity of most of the microsomal drug-metabolizing enzymes is higher in males than in females through androgen action which is readily impaire drug-metabolizing enzymes in male rats are thus manifested by two mechanisms; one is by impairment of androgen action and the other is by depression of the basic enzymic activity. Therefore, those effects of pathological states, observed only in male rats but not in females, are generally not seen in other species of animals, including man. The effects of starvation, hyperthyroidism, adrenal insufficiency, diabetes and morphine administration are cases where changes in metabolism are due solely to impairment of androgen action. In other pathological cases, those drug-metabolizing enzymes showing sex differences are depressed more markedly in male rats than those showing no clear sex difference. The author therefore recommends the use of female rats in the evaluation of the effects of pathological states on hepatic microsomal drug-metabolizing enzymes. Generally, changes in activity of the hepatic enzymes reflect closely the changes in the rates of drug metabolism in vivo. However, the protein-binding of drugs, hepatic blood flow and renal function are also known to affect the rate of drug metabolism and excretion in vivo, and therefore changes of these factors in pathological states should also be taken into consideration.