Iwao Yamazaki

Structure-activity relationships in the C-terminal part of luteinizing hormone releasing hormone (LH-RH)

Abstract Five new analogs of LH-RH(pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2), ( Des-Gly-NH 2 10 , Pro-methylamide9)-LH-RH, ( Des-Gly-NH 2 10 , Pro-propylamide9)-LH-RH, ( Des-Gly-NH 2 10 , Pro-ethanolamide9)-LH-RH, ( Des-Gly-NH 2 10 , Pro-pyrrolidineamide9)-LH-RH and ( Des-Gly-NH 2 10 , Pro-morpholineamide9)-LH-RH were synthesized and evaluated for the hormonal activity. The activities of these new analogs were compared with those of LH-RH and our previously reported highly potent analog, ( Des-Gly-NH 2 10 , Pro-ethylamide9)-LH-RH. The results demonstrate a significant contribution of the total chain-length of the hormone for the hormonal action.

Synthetic analogs of luteinizing hormone releasing hormone (LH-RH) substituted in position 6 and 10.

Abstract A series of peptide analogs of luteinizing hormone releasing hormone (LH-RH), altered at position 6 and 10, was synthesized and evaluated in vivo for the ability to induce ovulation in the diestrous rat and in vitro for ability to release pituitary luteinizing hormone and follicle stimulating hormone. All the analogs with D-amino acid substitutions at position 6, even those with large bulky side chain, exhibited an amazingly high potency compared with the parent hormone, LH-RH. On the basis of the biological activities, structure-activity relationships in the central part of this molecule were discussed in detail.

Effect of ipriflavone on glucocorticoid-induced osteoporosis in rats.

Ipriflavone, 7-isopropoxy-3-phenyl-4H-1-benzopyran-4-one, was administered orally for 12 weeks to male rats with prednisolone-induced osteoporosis. Microdensitometric analysis of a roentgenograph of the femurs revealed that ipriflavone increased the density of the distal metaphysis dose-dependently and tended to increase the density of the diaphysis. It also inhibited dose-dependently the decrease in the mechanical strength of the tibia, breaking strain and breaking energy, and the fractional content of ash in femurs. These results indicate that ipriflavone markedly suppresses bone resorption at the metaphysis where the content of trabecular bone with a rapid turnover rate is high, and possibly inhibits bone reduction at the diaphysis.

Some analogs of luteinizing hormone releasing hormone (LH-RH) having intense ovulation-inducing activity

Five new analogs of luteinizing hormone releasing hormone (LH-RH), des-Gly10-[Ala6]-LH-RH-ethylamide, des-Gly10-[D-Ala6]-LH-RH-ethylamide, des-Gly10-[α-aminoisobutyric acid6]-LH-RH-ethylamide, des-Gly10-[Phe5, D-Ala6]-LH-RH-ethylamide and des-Gly10-[Ile5, D-Ala6]-LH-RH-ethylamide were synthesized and evaluated for the ovulation-inducing activity in the rat, and it was found that the analogs, des-Gly10-[D-Ala6]-LH-RH-ethylamide and des-Gly10-[Phe5, D-Ala6]-LH-RH-ethylamide, were 50 times or more active than the original molecule.

Calcitonin secreting property of ipriflavone in the presence of estrogen

Calcitonin secretion is influenced by estrogen. In the present study, basal and calcium-stimulated serum calcitonin levels were reduced in ovariectomized rats, and replacement estrogen administered for 3 weeks increased both calcitonin levels to those in intact rats. Ipriflavone, 7-isopropoxy-3-phenyl-4H-1-benzopyran-4-one, alone did not influence either calcitonin level. However, ipriflavone and subeffective doses of estrogen administered simultaneously increased both levels; the increase depended upon the dose of ipriflavone. Furthermore, pretreatment with estrone resulted in greater calcitonin release in response to various doses of calcium and pretreatment with estrone and ipriflavone caused an even greater release. These findings indicate that ipriflavone increases the sensitivity of the thyroid gland to estrogen to secrete calcitonin in response to calcium.

Effect of ipriflavone on the response of uterus and thyroid to estrogen

Ipriflavone, 7-isopropoxy-3-phenyl-4H-1-benzopyran-4-one, was uterotropic in intact but not in ovariectomized rats. When it was administered simultaneously with estrone and estradiol-17 beta to ovariectomized rats, ipriflavone increased the uterotropic activities of both estrogens. The uterotropic activity of this compound in intact rats might be attributable to its action on the target organ of estrogen by augmenting the response to the hormone because none of the other possibilities for accelerating uterine growth such as gonadotropin-releasing, gonadotropic, and estrogen metabolism-retarding activities were demonstrated experimentally. In addition, ipriflavone increased the calcitonin releasing activity of estrone when these compounds were administered simultaneously to ovariectomized rats.

Syntheses and biological activities of analogs of luteinizing hormone releasing hormone (LH-RH)

Twenty analogs of luteinizing hormone releasing hormone (LH-RH or pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2), i.e., , , [Pro1]-, [Phe2]-, [3-Me-His2]-, [Lys2]-, [Arg2]-, [Ala4]-, [Thr4]-, [Gln5]-, [Cl-Tyr5]-, [di-Cl-Tyr7]-, [Gly7]-, [Ala7]-, [Val7] [Ile7]-, [Nle7]-, [Lys8]-, [Orn8]-, and [Ala10]-LH-RH, were synthesized by the fragment condensation method and some biological properties of these decapeptide amides were studied. On the basis of in,vitro and in,vivo biological activities of these analogs, structure-activity relationships were discussed.

Inhibitory effect of ipriflavone on osteoclast-mediated bone resorption and new osteoclast formation in long-term cultures of mouse unfractionated bone cells

SummaryTo study the effect of ipriflavone on osteoclast-mediated bone resorption and new osteoclast formation, we used an unfractionated bone cell culture system containing mature osteoclasts from femur and tibia of newborn mice. Ipriflavone (10−5 M) inhibited pit formation on dentin slices and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive (+) multinucleate cells (MNCs) in a 4-day culture period in which no increase in the number of TRAP(+)-MNCs was observed in the presence of 5% fetal bovine serum (FBS) and 10−8 M 1α,25-dihydroxy-vitamin D3 (1α,25(OH)2D3). During the following 12 days, both the total area of the pits and the number of TRAP(+)-MNCs increased in the control. Continuous treatment with ipriflavone also inhibited the increase in pit area during this period. These effects of ipriflavone were reversible. Furthermore, the differentiation of osteoclasts was examined when preexisting TRAP(+)-MNCs were removed by incubation in the absence of 1α,25(OH)2D3 for the initial 4 days in culture dishes without dentin slices. When 1α,25(OH)2D3 and ipriflavone were added to the medium on the 4th day, ipriflavone inhibited new TRAP(+)-MNC formation stimulated by 1α,25(OH)2D3 in a dose-dependent manner. However, pretreatment of the cells with ipriflavone before the addition of 1α,25(OH)2D3 did not inhibit TRAP(+)-MNC formation. These results indicate that ipriflavone inhibits both the activation of mature osteoclasts and the formation of new osteoclasts without affecting growth of TRAP-negative progenitor cells.

Inhibitory effect of ipriflavone on pit formation in mouse unfractionated bone cells

SummaryEffects of ipriflavone (7-isopropoxyisoflavone) on osteoclast-induced bone resorption were evaluated using an unfractionated bone cell culture system containing mature osteoclasts from the femur and tibia of newborn mice. When cells were cultured for 4 days on dentin slices in the presence of 5% fetal bovine serum and 10−8 M 1α,25(OH)2D3, ipriflavone (3 x 10−7-3 x 10−5 M) inhibited pit formation and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs). The lowest significant effect was observed at a concentration of 10−6 M. Unlike ipriflavone, calcitonin inhibited pit formation 4 days after the culture was started without affecting the number of TRAP-positive MNCs. Ipriflavone still inhibited pit formation when the culture period was 13 days, when new osteoclasts were expected to be formed. These findings suggest that ipriflavone inhibits new osteoclast formation and bone resorption at the cellular level.