Decapeptide luteinizing hormone releasing hormone in ovine pineal gland

Ovine pineal gland extracts were examined throughout the year for content and molecular form of immunoreactive (IMR) LH releasing hormone (LH-RH). The content of IMR LH-RH in pineal glands collected in spring and summer was 160-2230 pg/gland, while the content in pineal glands collected in autumn and winter was lower (31-39 pg/gland). Pineal gland IMR LH-RH, purified by affinity and Sephadex G-25 chromatography, yielded displacement curves parallel to those of hypothalamic IMR LH-RH and synthetic LH-RH in radioimmunoassays employing four antisera which require different regions of the decapeptide for effective binding, suggesting considerable similarities in the structure of the molecule. The majority of pineal gland IMR LH-RH behaved identically to hypothalamic IMR LH-RH and synthetic LH-RH on gel filtration, cation exchange chromatography, high-pressure liquid chromatography and cellulose thin-layer chromatography. However, a small amount of a less positively charged LH-RH species was also present in all pineal gland extracts. Our findings indicate that hypothalamic decapeptide LH-RH occurs in the ovine pineal gland.