INSITU HYBRIDIZATION STUDY OF OBESITY-ASSOCIATED ALTERATION IN GROWTH-HORMONE MESSENGER-RNA LEVELS

In order to investigate whether the impaired GH secretion associated with obesity is due to a pituitary disorder we studied GH mRNA levels by in situ hybridization in genetically obese and lean Zucker rats. The levels of GH mRNA were at least two fold lower in obese rats in comparison to that in lean controls as quantified by both the scanning of autoradiographs of tissue sections and Northern blot analysis. Quantification of somatotrophs revealed no significant difference in their number between lean and obese rat pituitaries. It is therefore likely that the attenuated GH mRNA levels in genetically obese Zucker rats are due to a decrease in GH transcripts per somatotroph rather than a result of a pituitary defect involving a preferential decrease in somatotroph population.