Esther J. Coy

Inhibition of adenosine 3′,5′-monophosphate accumulation in anterior pituitary gland in vitro by growth hormone-release inhibiting hormone

Summary 1 × 10 −7 M growth hormone-release inhibiting hormone (GH-RIH or somatostatin) leads to a 50% inhibition of adenosine 3′,5′-monophosphate (cyclic AMP) accumulation in anterior pituitary tissue during the first 2 min of incubation. This lowering of cyclic AMP levels is accompanied by inhibition of the release of immunoreactive growth hormone and thyrotropin. GH-RIH has also a marked inhibitory effect on the theophyline- and prostaglandin E 2 -induced accumulation of adenohypophyseal cyclic AMP.

Synthesis and biological properties of (D-Ala-6, des-Gly-NH2-10)-LH-RH ethylamide, a peptide with greatly enhanced LH- and FSH- releasing activity.

Abstract A nonapeptide analog of luteinizing hormone-releasing hormone (LH-RH), [D-Ala 6 , des-Gly-NH 2 10 ]-LH-RH ethylamide, was prepared by solid-phase methodology. The peptide was assayed against LH-RH in two in vivo systems and was found to be many times more potent than the naturally occurring hormone. In one of the tests, based on elevation of LH and FSH levels after infusion into immature male rats, the analog showed LH-releasing activity of 1600% and FSH-releasing activity of 1200% compared to LH-RH.

Solid phase synthesis of growth hormone-release inhibiting factor

Abstract The growth hormone-release inhibiting factor (GH-RIF) tetradecapeptide , was prepared by the cyclization of a linear, disulfhydryl peptide intermediate by treatment with potassium ferricyanide. The linear peptide was synthesized by an automated solid-phase technique. The cyclic material inhibited the secretion of radioimmunoassayable growth hormone in vitro at doses as low as 0.1 μg. A high molecular weight compound formed during the cyclization reaction and believed to be predominantly dimer also possessed considerable inhibitory activity.

Synthesis and biological properties of [Leu-6]-LH-RH and [D-leu-6,desGly-NH210]-LH-RH ethylamide

Abstract [Leu 6 ,desGly-NH 2 10 ]-LH-RH ethylamide and [Leu 6 ]-LH-RH, two analogs of LH-RH, were prepared by the solid phase method. LH- and FSH-releasing activity of these peptides was assayed against LH-RH by subcutaneous administration in immature male rats. When the integrated levels of LH and FSH over a 6 hr period after the injection were used as parameter of the LH- and FSH-releasing activities, the [Leu 6 ]-LH-RH showed LH-releasing activity of 9 times and FSH-releasing activity of 5 times greater than that of LH-RH. [Leu 6 ,desGly-NH 2 10 ]-LH-RH ethylamide showed LH- and FSH-releasing activities of 53.6 and 14.5 times greater, respectively, than that of LH-RH.

LH-releasing activity of potent LH-RH analogs in vitro.

Luteinizing hormone (LH)-releasing activity of 8 potent LH-releasing hormone (RH) analogs was investigated in primary cultures of anterior pituitary cells. Introduction of the C-terminal ethylamide modification into (D-Ala 6) - LH-RH were 90 and 100 times more active than LH-RH respectively. However the ethylamide derivatives of their 2 compounds were approximately 6 times less active than the parent peptides. It is suggested that the (D-Phe 6)- and (D-Trp 6) - peptides show great promise as structures on which to base the development of LH-RH antagonists.

Inhibition of growth hormone and thyrotropin release by growth hormone-release inhibiting hormone

Abstract Addition of increasing doses of synthetic growth hormone-release inhibiting hormone (GH-RIH) leads to a progressive decrease of the basal and N 6 monobutyryl cyclic AMP-,theophylline- and prostaglandin E 2 -induced release of immunoreactive growth hormone (GH) and thyrotropin (TSH) release from rat anterior pituitary cells in monolayer culture. A halfmaximal effect is measured at 3 × 10 −9 M GH-RIH while a maximal inhibition to 10–20% of the control level is found at 1 × 10 −7 M. Using rat hemipituitaries and measurement of GH release by both polyacrylamide gel electrophoresis and radioimmunoassay, a maximal effect of GH-RIH was found in the first 5 min of incubation. The inhibitory effect of GH-RIH on GH release remained constant for at least 3 h. GH-RIH does not affect the basal or induced release of prolactin and luteinizing hormone nor the high K + -induced release of GH and TSH.

Stimulatory and inhibitory analogs of luteinizing hormone releasing hormone

The isolation and the determination of the structure of porcine luteinizing hormone-releasing hormone (LHRH) (Fig. 1) in our laboratory (1–4) paved the way for its synthesis by our group (3,5) and by others (6). Intense activity which has been occurring since then in the field of synthesis of analogs of LHRH was caused by the desire to: (a) establish a relationship between the structure and biological activity of this hormone, (b) synthesize analogs with prolonged biological activity so that they would be more useful therapeutically than LHRH itself which has a very short halflife of about 2 min, and (c) develop inhibitory antagonistic analogs which would form the basis of new birth control methods.

Organ Distribution of Radioactivity and Disappearance of Radioactivity from Plasma After Administration of [3H] Luteinizing Hormone-Releasing Hormone to Mice and Rats

Whole-body autoradiography of amouse 5 min after an intrajugular injection of 43 nmoles of l-(4-[3H]pyro-Glu)-LH-RH (18.3 Ci/mmole) shows a large accumulation of radio-activity in the pituitary, subcutaneous tissue, intestinal wall, kidney, and bladder. Some radioactivity is also found in the liver, lungs, and heart, but no labeling is seen in the central nervous system. Direct measurements of radioactivity in different organs of the rat 5 min after injection of [3H] LH-RH also show that the highest accumulation of radioactivity is in the anterior pituitary gland, kidney, epididymal fat, and skin. Low labeling is measured in the posterior (including intermediate) lobe of the pituitary, pineal, liver, submaxillary gland, testis, adrenal, thyroid, and striated muscle. The pattern of plasma radioactivity after a single intravenous injection of [3H] LH-RH can be represented by the sum of four exponents, suggesting a four-compartment model of the disappearance of radioactivity from plasma. The metabolic clearance rate is 1.2 ml/min. The half-life of the first exponent (up to 10 min after injection) is about 7.5 min. 30 sec after injection of [3H] LH-RH, the radioactivity is distributed in a total volume of 26.5 ml (approximately 11% of body weight).

Gonadotropin-releasing activity of two highly active and long-acting analogs of luteinizing hormone-releasing hormone after subcutaneous, intravaginal, and oral administration.

The gonadotropin-releasing activities of two synthetic analogs of luteinizing hormone-releasing hormone (LH-RH), D-Ala6-des-Gly10-LH-RH ethylamide and D-Leu6-des-Gly10-LH-RH ethylamide were evaluated in immature female rats after subcutaneous, intravaginal, and oral administration. Maximal peaks of serum LH and follicle-stimulating hormone (FSH) levels after administration of both analogs by any of the three routes were obtained at 2 hours. Therefore, serum gonadotropin levels declined slowly, so that at 6 hours LH levels had returned to base line values, whereas FSH levels remained elevated for up to 10 hours. The integrated serum gaondotropin levels after LH-RH and both analogs over a 10-hour period indicated that D-Leu6-des-Gly10-LH-RH EA and D-Ala6-des-Gly10-LH-RH EA released more LH and FSH than did the LH-RH decapeptide. The intense and long-acting properties of these analogs in releasing LH and FSH suggest the possibility that they may be more useful therapeutically than LH-RH.

Luteinizing hormone-releasing hormone analogs with increased anti-ovulatory activity

Abstract A series of LH-RH antagonist analogs has been developed in which inhibitory activities have been increased to a potentially clinically useful level. The new peptides, which are typified by [N-acetyl-D-p-Cl-Phe 1,2 , D-Trp 3 , D-Phe 6 ,D-Ala 10 ]-LH-RH and [N-acetyl-D-Trp 1,3 ,D-p-Cl-Phe 2 ,D-Phe 6 , D-Ala 10 ]-LH-RH, most importantly contain new modification to positions 1, 2 and 10, and induce full blockade of ovulation at single doses as low as 10 μg per rat (50 μg/kg). Various ring substituents on D-Trp or D-Phe in position 1 or other D-amino acid replacements in position 10 did not significantly improve anti-ovulatory activity. Incorporation of N-Me-Leu in position 7 was slightly detrimental to activity.