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R. M. Popkin and H. M. Fraser

Summary. The hypothalamic—pituitary—ovarian axis of female rats was disrupted at the site of LHRH stimulation by active immunization against LHRH or at the site of LH action by active immunization against LH. Active immunization against LH was associated with an increase in pituitary LHRH receptors to levels comparable to control values at pro-oestrus whereas immunization against LHRH led to a marked reduction in receptor numbers. Ovarian LHRH receptor concentrations were increased by both treatments. It is concluded, therefore, that (1) LHRH receptors in the pituitary and ovary are not concomitantly controlled, and (2) pituitary receptor numbers are primarily under positive autoregulatory control by LHRH and that ovarian LHRH receptor concentrations may be under long-term influence of LH.

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Rachel M. Popkin, H. M. Fraser and R. G. Gosden

Summary. Hyperstimulation of pituitary function using daily injections of 50, 500 or 5000 ng LH-RH agonist for 3 weeks or hypostimulation by immunoneutralization of endogenous LH-RH led to disrupted oestrous cycles and profound changes in ovarian morphology. Despite this, the number of pituitary and ovarian LH-RH receptors remained within the range found in normally cyclic animals. Autoradiography confirmed that specific binding was located in theca, granulosa and luteal cells.

These results suggest that autoregulation of pituitary and ovarian LH-RH receptors is not of primary importance in the cyclic female rat.

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H. J. Stewart, D. S. C. Jones, J. C. Pascall, R. M. Popkin and A. P. F. Flint

Page Introduction 2 Structures of genes and mRNA molecules 2 Structure of genes 2 Sequences of promoters and enhancers 3 Signals for terminating RNA synthesis 5 Structure of mRNA molecules 5 Structure of genes coding for reproductive polypeptide hormones and hypothalamic releasing factors 7 Structure of gonadotrophin genes 7 Structure of placental lactogen, prolactin and growth hormone genes 10 Structure of the LHRH gene 12 Inhibin, activin and Müllerian duct-inhibiting hormone 13 Localization of gene products by in-situ hybridization 16 Pre- and post-translational processing 18 Pretranslational processing: differential splicing of RNA 18 Post-translational processing 18 Steroidogenic enzymes and steroid sulphatase 20 Steroid hormone receptors 22 Steroid receptor primary structure: amino acid sequences derived from cloned DNA 23 Steroid hormone receptors and oncogenesis 26 Mechanism of binding of receptors to DNA—the finger hypothesis 27 DNA sequences recognized by steroid receptors in eukaryotic cells 28 Fertilization and early development 30 Expression of