Developmental Changes in the Expression of the Growth Hormone Receptor Messenger Ribonucleic Acid and Protein in the Bovine Ovary1

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Abstract
By reverse transcription-polymerase chain reaction, the transcript of the growth hormone receptor (GHR) was demonstrated in oocytes, follicular cells, and corpus luteum of the bovine ovary. Immunoblotting using the monoclonal antibody mAb 263 resulted in a distinct protein band at 120 kDa, confirming that translation of the mRNA takes place in the same cells. Nonradioactive in situ hybridization revealed that distribution of the mRNA encoding GHR was correlated with the developmental stage of the follicle. Whereas in primordial and primary follicles the oocyte showed distinct amounts of the transcript encoding GHR, in tertiary follicles the mRNA was predominantly localized in the cells of the cumulus oophorus. GHR mRNA was also expressed in the large granulosa lutein cells, in the germinal epithelium, and in the endothelial cells of ovarian vessels. Colocalization of the GHR protein showed a distribution pattern identical to that of the mRNA. In calves, oocyte and follicle cells changed GHR expression in the same way as in the adult ovary. During embryonic development of the ovary, distinct amounts of the mRNA encoding GHR were found in primordial follicles shortly before birth. Our results imply that the GHR is involved in ovarian ontogenesis, especially in early folliculogenesis.