Effect of chronic alcohol consumption on ethanol and acetaldehyde metabolism

Hepatic metabolism of ethanol to acetaldehyde by the alcohol dehydrogenase (ADH) pathway is associated with the generation of reducing equivalents as NADH. Conversely, reducing equivalents are consumed when ethanol oxidation is catalyzed by the NADPH dependent microsomal ethanol oxidizing system (MEOS). Since the major fraction of ethanol metabolism proceeds via ADH and since the oxidation of acetaldehyde also generates NADH, an excess of reducing equivalents is produced. This explains a variety of effects following acute ethanol administration, including hyperlactacidemia, hyperuricemia, enhanced lipogenesis and depressed lipid oxidation. To the extent that ethanol is oxidized by the alternate MEOS pathway, it slows the metabolism of other microsomal substrates. Following chronic ethanol consumption, adaptive microsomal changes prevail, which include enhanced ethanol and drug metabolism, and increased lipoprotein production. Eventually, injury develops with alterations of the rough endoplasmic reticulum and structural and functional abnormalities of the mitochondria.

Initial response of human thyroid, adrenal cortex, and adrenal medulla to acute cold exposure

Human subjects were exposed nude to a mild cold of 10 to 15 °C for 1 hour in summer. Free catecholamine excretion in the urine increased markedly during cold exposure. The level of plasma cortisol rose slightly but significantly at the end of cold exposure. Plasma PBI did not change significantly. A rise in blood pressure, a decrease in heart rate, a rise in rectal temperature, cold diuresis, and an increase in urinary electrolyte excretion and hemoconcentration were observed as the initial responses to cold exposure. The physiological role played by endocrine glands in these initial responses is discussed. A preliminary experiment of the same type carried out in winter is described, and some differences in the experimental results from those obtained in summer are noted.