Ann Ruhmann-Wennhold

Disappearance rates of exogenous and endogenous ACTH from rat plasma measured by bioassay and radioimmunoassay

The disappearance rates of ACTH in rat plasma were measured by both radioimmunoassay and bioassay. αh-ACTH (Li) was the standard in both assays. αh-ACTH (Li) (50 mU) given intravenously disappeared with a half time of 2.9 min by bioassay and 4.1 min by radioimmunoassay. Endogenous ACTH in stressed 14-day adrenalectomized rats had a t12 of 1.7 min by bioassay and 3.6 min by radioimmunoassay. Intact stressed rats showed a similar decrease in ACTH as measured by radioimmunoassay with a half-life of 4.1 min. In all cases the decay curve was biphasic when determined immunologically, the second portion being longer than the first. It is possible that ACTH fragments that are biologically inactive appear in rat plasma under conditions of increased ACTH output.

PLASMA ACTH LEVELS IN STRESSED AND NONSTRESSED ADRENALECTOMIZED RATS

Following adrenalectomy there is a triphasic response of ACTH secretion characterized by an initial high rise immediately following the adrenalectomy, secondary to the stress of the procedure. This is followed by a fall to resting ACTH secretion until a steady state is reached 1 to 2 weeks following adrenalectomy at levels about 10 times normal. The ability to respond to stress with increased ACTH secretion is not lost at any time following adrenalectomy.

Effect of lipid extraction, adrenalectomy, and cortisol upon free radical formation by rat lung microsomes

Abstract Free radical formation and superoxide anion production by rat lung microsomes have been determined by measurement of conversion of epinephrine to adrenochrome in vitro . There was a marked increase in Superoxide anion production by the microsomes following extraction with 10% aqueous acetone as has been seen previously following adrenalectomy in animals exposed to 100% oxygen. When the extracted lipid was added back to the extracted microsomes there was a significant reduction in the superoxide anion production similar to the reduction seen following cortisol administration to adrenalectomized animals.

An effect of corticosteroids and 100% oxygen on aryl hydrocarbon hydroxylase, cytochrome-c reductase, and free radical formation by rat lung microsomes☆

Activity of aryl hydrocarbon hydroxylase (AHH), cytochrome c-reductase, and NADPH oxidase, and epinephrine oxidation to adrenochrome were determined in lung microsomes from intact, adrenalectomized, and adrenalectomized cortisol-treated female rats under ambient and hyperoxic conditions. Microsomal adrenochrome formation, which is initiated by superoxide anion or other free radicals, was increased by adrenalectomy and decreased by cortisol treatment. Exposure of animals to 100% oxygen caused a further increase in adrenochrome formation. NADPH-cytochrome c-reductase and AHH activities were increased in incubations of microsomes from animals which had received cortisol in vivo while adrenalectomy led to decreases activity. NADPH oxidase activity was increased by cortisol in lung microsomes in the presence of either epinephrine or cytochrome c. Epinephrine conversion to adrenochrome in the presence of lung microsomes was blocked by SOD, but NADPH-cytrochrome c-reductase and AHH activity were unaffected.

Testosterone Inhibition of Estradiol-Induced Stimulation of Adrenal 11β- and 18-Hydroxylation

Summary Adrenal homogenates from intact and castrated male and female rats treated with 1 μg 17β-estradiol iv were tested for ability to convert exogenous DOC to B and 18-OH DOC. Estradiol, which causes a significant increase in hydroxylating capacity in intact female rats, produced no such increase in intact males. Orchiectomized males, however, responded to estradiol with increased ability to hydroxylate. The estradiol response was lost after administration of testosterone to both orchiectomized males and intact females.

Effects of Testosterone and Estradiol in Vivo on Hepatic Cortisol Metabolism in Vitro

Summary Estradiol inhibited the ability of the liver parenchymal cell to transform Cortisol to reduced metabolites whereas testosterone increased both reductive and oxidative metabolism of cortisol. The stimulatory effect on β–hydroxylation was not due to an increase in cytochrome P–450 content.