R.M.G. Nair

Structure of the porcine LH- and FSH-releasing hormone. I. The proposed amino acid sequence

Summary The complete amino acid sequence of porcine LH- and FSH- releasing hormone has been provisionally determined by the use on a micro-scale of the combined Edman-dansyl procedure coupled with the selective tritiation method for C-terminal analysis. These procedures were used directly on the digestion products of LH-RH with chymotrypsin and thermolysin, without separation of the fragments. Additional data were provided by high resolution mass spectral fragmentation of LH-RH. On the basis of these results, we propose the following decapeptide sequence for LH-RH: (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2.

Isolation and properties of the FSH and LH-releasing hormone☆

Abstract LH-releasing hormone (LH-RH) was obtained in apparently a homogeneous state from extracts of pig hypothalami. The LH-RH preparation isolated has FSH-releasing hormone (FSH-RH) activity, which appears to be intrinsic to LH-RH. The amino acid composition of LH-RH/FSH-RH as determined on acid hydrolysates is: His 1, Arg 1, Ser 1, Glu 1, Pro 1, Gly 2, Leu 1 and Tyr 1. The hormone isolated stimulates the release of FSH and LH in vivo and in vitro in doses of a few nanograms. This polypeptide appears to represent the hypothalamic hormone which controls the secretion of both LH and FSH from the pituitary.

Isolation and structure of hypothalamic MSH release-inhibiting hormone***

Summary MSH-release inhibiting hormone (MRIH) activity in bovine hypothalamic extracts, concentrated over 11,000-fold by gel filtration on Sephadex, was further purified by thin-layer chromatography. Two MRIH-active peptides were isolated; one showed a high and the other much weaker MRIH activity. The amino acid sequence of the main MRIH-active peptide, as determined by Edman degradation combined with the dansyl method, was shown to be prolyl-leucyl-glycine amide. These findings were confirmed by mass spectra. Synthetic L-Pro-L-Leu-glycine amide and the natural main MRIH-active peptide showed similar biological activities, chromatographic and electrophoretic mobilities, and mass spectral fragmentation patterns. This work indicates that the structure of bovine MRIH is L-Pro-L-Leu-Gly. NH 2 .

Synthesis of the porcine LH- and FSH-releasing hormone by the solid-phase method☆

The decapeptide (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, corresponding to the amino acid sequence of the porcine LH- and FSH-releasing hormone (LH-RHFSH-RH) has been synthesized by the solid phase method. After repurification, the synthetic product showed the same physico-chemical and biological properties as natural porcine LH-RHFSH-RH.

Structure of the porcine LH-and FSH-releasing Hormone.: I. The proposed amino acid sequence0110 0

AbstractThe complete amino acid sequence of porcine LH- and FSH-releasing hormone has been provisionally determined by the use on a micro-scale of the combined Edman-dansyl procedure coupled with the selective tritiation method for C-terminal analysis. These procedures were used directly on the digestion products of LH-RH with chymotrypsin and thermolysin, without separation of the fragments. Additional data were provided by high resolution mass spectral fragmentation of LH-RH. On the basis of these results, we propose the following decapeptide sequence for LH-RH: (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2.

Distribution, half-life, and excretion of 14 C- and 3 H-labeled L-prolyl-L-leucyl-glycinamide in the rat.

H-Pro-Leu-Gly-NH2, a potentinhibitor of melanocyte stimulating hormone (MSH) release [MSH-release inhibiting factor (MIF)], was labeled with 14C-leucine or 3H-proline and injected i.v. into rats. H-Pro-14C-Leu-Gly-NH2 was found to have a half-life of approximately 9 min and to be distributed in a space greater than that of the plasma volume. Relatively little radioactivity and no intact H-Pro-Leu-Gly-NH2 could be found in the urine 1 h after administration. 3H- and 14C-labeled-H-Pro-Leu-Gly-NH2 accumulated in the pineal, pituitary, kidney, liver, and adrenals; the elevated tissue to plasma ratio in the pineal, along with the identification of unchanged H-Pro-Leu-Gly-NH2 there, suggests the possibility of a direct influence of the hypothalamus upon the pineal gland.

Isolation and structure of another hypothalamic peptide possessing MSH-release-inhibiting activity

Abstract A second peptide with the biological activity of an MSH-release-inhibiting factor (MIF) and with the amino acid composition His 1, Arg 1, Pro 1, Gly 1, Phe 1 was isolated from bovine hypothalami. This pentapeptide, when subjected to the combined Edman-dansyl degradation, yielded the sequence Pro-His-Phe-Arg-Gly-NH 2 , which was confirmed by derivatisation and mass spectral fragmentation. A peptide of similar structure was then synthesized. The chromagraphic and electrophoretic mobilities, biological activities, and mass spectral fragmentation patterns of the synthetic and natural peptides were compared and found to be similar. These studies suggest the existence of a hypothalamic pentapeptide, H-Pro-His-Phe-Arg-Gly-NH 2 , possessing MIF-activity.

Delayed Disappearance of 14C-Labeled-Pro-Leu-Gly-NH2 from the Blood of Hypophysectomized Rats

The disappearance of radioactivity after the injection of 14C-labeled-Pro-Leu-Gly-NH2, an MSH release-inhibiting factor (MIF-I), was measured in rats which had been subjected to various procedures. Delayed disappearance of the radioactivity to a small but statistically highly significant extent was found in hypophysectomized rats compared to rats with an intact pituitary. Pinealectomy and adrenalectomy did not change the half-time disappearance. Dehydration, hypothalamic destruction, or administration of excess saline, MSH, and large amounts of unlabeled MIF-I were all used as control procedures. These failed to demonstrate the mechanism by which the prolonged disappearance occurred, but did raise other questions. The half-time disappearance of tritiated inulin was not significantly different in hypophysectomized or intact rats. The results indicate that the absence of the pituitary gland prolongs the half-time disappearance of radioactivity from the blood of rats injected with labeled MIF-I.