Characterization of the translated products of the alternatively spliced luteinizing hormone receptor in the ovine ovary throughout the oestrous cycle

Abstract

The luteinizing hormone receptor (LHR) is alternatively spliced. It is not known if the alternatively spliced mRNAs are translated in vivo, or indeed if they have any vital role to play. The B splice form has been detected in every species examined, and it encodes a putative protein with a high affinity LH/CG binding domain but no trans-membrane or intra-cellular domains. We raised antisera that recognize the putative protein of the B form, and the closely related G form, and showed that the B form mRNA is translated in the ovine ovary, but not kidney or liver. It localized to the luteal cytosolic and microsomal fractions and the levels declined during regression induced by treatment with prostaglandin F2alpha. We examined alternative splicing by RNase protection analyses and RT-PCR analyses of healthy pre-ovulatory follicles, atretic or steroidogenically-inactive follicles, and of newly formed, mid-luteal and regressing corpora lutea. There was approximately 5-fold more B form mRNA than A form. Thus we have evidence that the LHR B form is translated in vivo, but no evidence that alternative splicing of the LHR mRNA is differentially regulated, throughout the oestrous cycle.