Benefits of glucose and oxygen in multidose cold cardioplegia.

We tested the effects of glucose and oxygen in cardioplegic solutions on myocardial protection in the isolated perfused working rat heart. Recovery from 2 hours' hypothermic (8 degrees C) cardioplegic arrest was examined in 93 hearts. Cardioplegic solution, which was delivered every 15 minutes, was supplemented with glucose 28 mmol/L as a substrate or sucrose 28 mmol/L as a nonmetabolizable osmotic control; it was equilibrated with either 98% oxygen or 98% nitrogen, both with 2% carbon dioxide. Four combinations of hyperkalemic cardioplegic solution were studied: nitrogen-sucrose, nitrogen-glucose, oxygen-sucrose, and oxygen-glucose. During hypothermic arrest, oxygenation of cardioplegic solution greatly reduced myocardial lactate production and prevented ischemic contracture as indicated by coronary vascular resistance. Glucose increased lactate production modestly but significantly only when the cardioplegic solution was nitrogenated. Although end-arrest myocardial adenosine triphosphate and creatine phosphate were greatly increased by oxygenation of cardioplegic solution (p less than 0.005), we could not detect improved preservation of these high-energy phosphates by glucose. Averaged over reperfusion, percent recovery of cardiac output for the nitrogen-sucrose, nitrogen-glucose, oxygen-sucrose, and oxygen-glucose solutions was 32.3% +/- 6.1%, 45.9% +/- 4.6%, 44.5% +/- 4.6%, and 62.2% +/- 4.5%, respectively. Oxygenation of the glucose solution or addition of glucose to the oxygenated solution significantly improved recovery of cardiac output. The benefits of glucose and oxygen were additive, so that the oxygen-glucose cardioplegic solution provided the best functional recovery. We conclude that the addition of glucose to the fully oxygenated multidose cold cardioplegic solution improves functional recovery without increasing lactate production during arrest.

Partial characterization and ontogeny of renal cytosolic glucocorticoid receptors in mouse kidney.

The glucocorticoid receptor (GR) was partially characterized in mouse renal cytosol. A sensitive and reproducible [3H]dexamethasone binding assay suitable for use with small quantities of cytosolic protein, was developed. Studies defined the optimal equilibrium binding conditions, metabolism of [3H]dexamethasone in adult renal cytosol, specificity of binding of the GR, and molecular weight of the GR-[3H]dexamethasone complex by gel filtration chromatography. The assay was subsequently used to measure the renal GR during different stages of foetal and postnatal development, as well as in glomerular and renal tubular preparations from adult mice. An almost linear increase in GR occurred from day 13 to day 18 of gestation with levels rising from 100 to 201 fmol/mg cytosol protein; this was followed by a sharp rise in receptor concentration just after birth to 343 fmol/mg cytosol protein. Adult levels, 410-433 fmol/mg cytosol protein, were reached by 2 weeks after birth. The equilibrium dissociation constants (Kd) of the [3H]dexamethasone-receptor complex were similar in adult and in embryonic cytosols (range, 2.8-11.8 nM; mean +/- SD = 6.5 +/- 2.9 nM). Specific binding was assessed to be 3- to 5-fold greater in tubular than in glomerular preparations. These data on the localization and ontogeny of GR during murine metanephric development provide a basis for study of glucocorticoid-mediated effects on various models of congenital and acquired renal disease.

Effects of H2-antagonists on androgen imprinting of male hepatic functions.

Many of the sex-differentiated functions of the liver of adult male rats depend upon the occurrence of neonatal androgen imprinting, a brief surge of androgen early in life. We investigated whether androgen imprinting is necessary for the development and maintenance of levels of a microsomal enzyme, estrogen-2-hydroxylase (E-20Hase), and a male-specific cytosolic estrogen binder (MEB) which are higher in adult male than in adult female rats. Cimetidine, a weakly antiandrogenic H2 blocker, was administered to pregnant and lactating rats from day 12 of gestation through weaning on day 21. Livers of male progeny, 120-150 days of age, were assayed for E-2OHase and MEB activity; a maternal dose equivalent to 2.5 times the usual human dose inhibited MEB activity in the levels of the offspring by 40% but had no effect on E-2OHase. However, a higher dose (5 times the human dose) was effective in reducing the E-2OHase activity by 50%. Rats whose mothers had received either no drug or an equivalent dose of ranitidine, another H2 blocker without antiandrogenic activity, were used as controls. The groups were not different in hepatic cytosolic androgen receptor content, body weight, or serum testosterone. In other studies, the requirement of neonatal androgen imprinting for full expression of adult levels of MEB and E-2OHase was determined. Female rats, which have low levels of E-2OHase and undetectable levels of MEB, were given androgen on day 1, on day 60 after ovariectomy, or at both times. Levels of E-2OHase equivalent to those in adult males were induced in females receiving both androgen treatments, whereas either treatment alone induced E-2OHase to the level of that in males castrated at adulthood or neonatally, which is about 50% that in normal male controls. In addition, MEB levels were induced in females to 85% of that in normal males by both androgen treatments and to 50% by administration of androgen to adult females or to adult males castrated neonatally. Administration of androgen to females during the neonatal period only did not induce MEB. We conclude that both MEB and E-2OHase require androgen imprinting for full expression in adult male rats.