Biomedical subjects

M E Bligh

Publications and source records attributed to M E Bligh.

3 recordsLinked to original sources

PubMed1993

Aldosterone diurnal rhythm in the rat: a question of cross-reactivity?

Radioimmunoassay (RIA) of plasma aldosterone (ALDO) can be hampered by cross-reactivity with plasma corticosterone (CORT). The purpose of this study was to determine and adjust for CORT crossreactivity when assaying for ALDO in blood samples taken throughout a 24-h period. Plasma was obtained from 10 adrenalectomized male Sprague-Dawley rats. Corticosterone-free plasma was spiked with 0, 50, 75, 100, 150, 200, and 300 ng/ml CORT. Aldosterone determination was performed by RIA. An equation for ALDO concentration adjusted for plasma CORT concentration was calculated (ALDO = measurable ALDO - 0.377 x CORT - 5.324). Twenty male Sprague-Dawley rats were adapted to a 12/12 light/dark cycle (lights on at 0900 h). They were divided into two groups based on body weight. Blood samples were obtained every 4 h beginning at 0900 h from rats in group 1 and beginning at 1100 h from rats in group 2. Distinct diurnal CORT and ALDO rhythms were observed. Corticosterone levels were highest at 2100 h (131.8 +/- 17.8 ng/ml) and lowest at 1300 h (04.6 +/- 1.8 ng/ml). Aldosterone levels were highest at 1900 h (276.50 +/- 53.60 pg/ml) and lowest at 1500 h (27.53 +/- 6.84 pg/ml). Corticosterone and ALDO levels were often significantly correlated (r > 0.60), but not at times when CORT and ALDO levels were at their highest. These results suggest that ALDO and CORT may be regulated by different mechanisms or may have a regulatory influence upon each other throughout the day/night cycle.

Aldosterone↗

PubMed1993

Corticosterone modulation of dietary selection patterns.

Effects of corticosterone (CORT) supplementation on ad lib macronutrient selection and selection following food deprivation were examined in male adrenalectomized (ADX) Sprague-Dawley rats. The ADX rats self-administered CORT from drinking solutions of 0 microgram/ml, 20 micrograms/ml, or 40 micrograms/ml. Adrenalectomy attenuated weight gain, which CORT failed to completely restore. After 6 days, rats were deprived for 0 or 24 h. Adrenalectomy attenuated weight loss during deprivation; CORT failed to restore weight loss. Adrenalectomy reduced ad lib protein intake, which CORT failed to restore. Carbohydrate and fat intakes were not affected by ADX; CORT (40 micrograms/ml) increased fat intake. During the first hour of refeeding, ADX attenuated protein intake; CORT failed to restore intake. Corticosterone-supplemented rats consumed more fat than unsupplemented ADX rats. Over 24 h, unsupplemented, deprived ADX rats consumed less fat and calories than all other deprived groups. These results suggest that CORT affects weight gain in lean rats and modulates macronutrient selection both ad lib and following food deprivation.

Adrenalectomy↗

PubMed1990

Adrenal modulation of the enhanced fat intake subsequent to fasting.

Elevations in corticosterone have been linked with the enhanced fat appetite of genetically obese Zucker rats. The present study set out to describe the effects of elevations in corticosterone in adult male Sprague-Dawley rats. Previous studies have shown that food deprivation leads to a time-dependent increase in basal corticosterone concentrations. It was predicted that rats would select a high fat diet during initial refeeding subsequent to a 24-hour fast and more severe food deprivation (48 hours) would promote greater fat consumption. Dependence upon adrenal hormones for this enhanced fat intake was examined with adrenalectomized animals. It was hypothesized that adrenalectomy would prevent the increase in fat intake seen in intact animals. Two experiments were performed. In the first, rats were given access to three separate macronutrient sources and allowed to self-select a diet for 7 days. They were then divided into groups and deprived of food for 0, 24, or 48 hours. At the end of the restriction period each rat was tail bled and macronutrient access was restored. Intakes were measured and blood samples taken at 1, 3, 6, 12, and 24 hours following restored access. During the first hour of refeeding, food-deprived animals ate significantly more fat than nondeprived animals. The enhanced fat intake was positively correlated with the elevations in corticosterone observed at the start of the refeeding period (r = .72). In the second experiment, rats were allowed to self-select a diet for 9 days. On Day 10 the rats received either bilateral adrenalectomies or sham operations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗