SOMATOGENIC AND LACTOGENIC BINDING-SITES IN RAT-BRAIN AND LIVER - QUANTITATIVE AUTORADIOGRAPHIC LOCALIZATION

The distribution of somatogenic and lactogenic binding sites in female and male rat brain as well as in liver was studied by quantitative re ceptor autoradiography using I-125-human growth hormone (I-125-hGH) as a ligand. Quantitative measurement of binding sites for I-125-hGH sho wed differences in the levels of these sites in the female and male br ain and liver. Moreover, regional differences in the brain were also o bserved in each sex. In the female brain high levels of I-125-hGH bind ing sites were found in the choroid plexus. Intermediate levels were o bserved in the striatum, the hypothalamus and the hippocampus, whereas low levels of these sites were found in the central gray, the tempora l, the piriform and the entorhinal cortices. In the male brain high le vels of I-125-hGH binding sites were detected in the choroid plexus. I ntermediate levels were observed in the parietal cortex, the hypothala mus and the hippocampus, whereas low levels were found in the tegmentu m, the temporal cortex and the striatum. Quantification of I-125-hGH b inding sites in the liver revealed higher levels in the female than in the male liver. In general, higher levels of binding sites (16%-77%) were observed in the female than in the male tissues. The quantificati on of rat growth hormone (rGH) by radioimmunoassay was also performed in this study. Varying amounts of rGH immunoreactivity were detected i n the different brain regions, with the highest levels of rGH-like mat erial being found in the midbrain and cortex of both sexes. Moreover, higher levels of rGH-like material were observed in the female than in the male brain. Thus, sex differences in the levels of both I-125-hGH binding sites and rGH-like material were observed between the female and male rat brain.