Immunoreactive LHRH in Chronic Starved Rats

Summary

The effects of chronic starvation (1/4 of ad libitum food intake) for 21 or 30 days were studied on the hypothalamic and serum concentrations of LHRH, the pituitary and serum concentrations of LH, and the weights of the anterior pituitary, ovary and uterus in adult female Wistar rats (chronic starved group, CSG). Control female rats were fed ad lib. for the same periods (control group, CG). On day 22 or 31, half of the rats of each group were weighed and sacrificed by decapitation. Since there were no difference on above parameters between the experiments on 22nd and 31st day, the results were combined for each parameters. At the time of sacrifice, the body weight of CSG was on the average 44% lower than that of CG rats, and also marked reduction in anterior pituitary (44%), ovarian (61%) and uterine weights (69%) was observed. Serum LH concentrations (mean ± SE; 5.67±0.67 versus 33.30±6.00 ng/ml, P < 0.001) and pituitary LH content (286.7±19.4 vs 451.0±32.8 μg, P < 0.001) were significantly decreased in CSG than in CG rats. However, pituitary LH concentration was not reduced because of the proportional reduction to the pituitary weight of CSG rats. Hypothalamic immunoreactive LHRH (IR-LHRH) content in CSG showed a significant increase as compared to CG rats (5.77±0.52 vs 4.41±0.27 ng/hypothalamic extract, P < 0.05). This hypothalamic LHRH immunoreactivity of CSG rat was eluted in identical fractions with that extract of CG rat and synthetic LHRH on Sephadex G-25 chromatography, and the dilution gave a displacement curve parallel to that with the standard. However, serum IR-LHRH concentrations in CSG were not significantly different from CG (5.2±0.7 vs 5.1±0.6 pg/ml). These data suggest that the reduction of LH secretion in chronic starvation was due to the inhibition of the release of hypothalamic LHRH.

Key-Words

Starvation - LHRH - LH - Rat