Synthesis of a series of stromelysin-selective thiadiazole urea matrix metalloproteinase inhibitors

The synthesis and enzyme inhibition data for a series of thiadiazole urea matrix metalloproteinase (MMP) inhibitors are described. A broad screening effort was utilized to identify several thiadiazoles which were weak inhibitors of stromelysin. Optimization of the thiadiazole leads to include an alpha-amino acid side chain with variable terminal amide substituents provided a series of ureas which were moderately effective stromelysin inhibitors, with Ki's between 0.3 and 1.0 microM. The most effective analogues utilized an L-phenylalanine as the amino acid component. In particular, unsubstituted 46 had a Ki of 710 nM, while the p-fluoro analogue 52 displayed increased potency (100 nM). Stromelysin inhibition was further improved using a pentafluorophenylalanine substituent which resulted in 70, a 14 nM inhibitor. While gelatinase inhibition was generally poor, the use of 1-(2-pyridyl)piperazine as the amide component usually provided for enhanced activity, with 71 inhibiting gelatinase with a Ki of 770 nM. The combination of this heterocycle with a p-fluorophenylalanine substituent provided the only analogue, 69, with collagenase activity (13 microM). The SAR for analogues described within this series can be rationalized through consideration of the X-ray structure recently attained for70 complexed to stromelysin. Uniquely, this structure showed the inhibitor to be completely orientated on the left side of the enzyme cleft. These results suggest that thiadiazole urea heterocycles which incorporate a substituted phenylalanine can provide selective inhibitors of stromelysin. Careful selection of the amide substituent can also provide for analogues with modest gelatinase inhibition.

Structural characterizations of nonpeptidic thiadiazole inhibitors of matrix metalloproteinases reveal the basis for stromelysin selectivity

The binding of two 5-substituted-1,3,4-thiadiazole-2-thione inhibitors to the matrix metalloproteinase stromelysin (MMP-3) have been characterized by protein crystallography. Both inhibitors coordinate to the catalytic zinc cation via an exocyclic sulfur and lay in an unusual position across the unprimed (P1-P3) side of the proteinase active site. Nitrogen atoms in the thiadiazole moiety make specific hydrogen bond interactions with enzyme structural elements that are conserved across all enzymes in the matrix metalloproteinase class. Strong hydrophobic interactions between the inhibitors and the side chain of tyrosine-155 appear to be responsible for the very high selectivity of these inhibitors for stromelysin. In these enzyme/inhibitor complexes, the S1' enzyme subsite is unoccupied. A conformational rearrangement of the catalytic domain occurs that reveals an inherent flexibility of the substrate binding region leading to speculation about a possible mechanism for modulation of stromelysin activity and selectivity.

Synthetic matrix metalloproteinase inhibitors and tissue inhibitor of metalloproteinase (TIMP)-2, but not TIMP-1, inhibit shedding of tumor necrosis factor-alpha receptors in a human colon adenocarcinoma (Colo 205) cell line

The solubilization of plasma membrane receptors through proteolytic cleavage of the ligand binding domain at the cell surface is an important mechanism for regulating cytokine function and receptor signaling. The inhibition of the shedding of a variety of receptors by synthetic inhibitors of the matrix metalloproteinases (MMPs) implicates metalloproteinases in this regulatory event. We examined the effects of two naturally occurring tissue inhibitors of metalloproteinases, TIMP-1 and TIMP-2, and several synthetic MMP inhibitors (MMPIs) on the shedding of both tumor necrosis factor alpha receptor type I (TNFalpha-RI; Mr 55,000) and TNFalpha-RII (Mr 75,000) by the Colo 205 human colon adenocarcinoma cell line. Culture of Colo 205 cells for 48 h resulted in the shedding of both TNFalpha-RI and TNFalpha-RII, as determined by ELISA. The shedding of TNFalpha receptors was not affected by TIMP-1 or protease inhibitors aprotinin, pepstatin, or leupeptin but was inhibited in a dose-dependent manner by the following synthetic MMPIs: batimastat and marimastat (BB-94 and BB-2516, respectively, British Biotech, Inc.); CT1418 (Celltech Therapeutics); CGS27023A (Novartis Pharmaceuticals); and RO31-9790 (Roche), with IC50s ranging from 3.2 to 38.0 microM. Similarly, TIMP-2 from two different sources reproducibly inhibited the shedding of both TNFalpha-RI and TNFalpha-RII in a dose-dependent manner (IC50 = 286 +/- 33 nM for TNFalpha-RI shedding and 462 +/- 52 nM for shedding of TNFalpha-RII). The inhibition of TNFalpha-RI shedding was confirmed in the SW626 human ovarian adenocarcinoma cell line. The synthetic MMPIs and TIMP-2, but not TIMP-1, also caused a dose-dependent increase in the number of TNFalpha receptors retained on the surface of Colo 205 cells, as determined by flow cytometry. Inhibition of TNFalpha receptor shedding with TIMP-2 occurs at molar concentrations 10-100 times less than those required with low molecular weight, synthetic MMPIs but at concentrations greater than those required to inhibit collagen degradation. Modulation of TNFalpha receptor shedding by TIMP-2 could have important implications for the pleiotropic effects of TNFalpha in both normal and malignant cells and for the pharmacological activity of synthetic MMPIs.

Modulation of bovine microvascular endothelial cell proteolytic properties by inhibitors of angiogenesis

A tightly controlled increase in extracellular proteolysis, restricted both in time and space, is an important component of the angiogenic process, while anti-proteolysis is effective in inhibiting angiogenesis. By focussing on the plasminogen activator (PA)-plasmin system, the objective of the present studies was to assess whether previously described inhibitors of angiogenesis modify bovine microvascular endothelial cell proteolytic properties. We demonstrate that although synthetic angiostatic steroids (U-24067 and U-42129), heparin, suramin, interferon alpha-2a, and retinoic acid are all inhibitors of in vitro angiogenesis, each of these agents has distinct effects on the plasminogen-dependent proteolytic system. Specifically, angiostatic steroids and interferon alpha-2a reduce urokinase-type PA (u-PA) and PA inhibitor-1 activity, while heparin and retinoic acid increase u-PA activity. Suramin reduces cell-associated u-PA activity and greatly increases PAI-1 production at doses which induce monolayer disruption. These findings demonstrate that a spectrum of alterations in extracellular proteolysis is associated with anti-angiogenesis, and that anti-angiogenesis and anti-proteolysis are not necessarily correlated. A reduction in extracellular proteolysis would be expected to reduce invasion, whereas an increase in proteolysis might modulate the activity of inhibitory cytokines, which in turn could reduce endothelial cell proliferation and migration and inhibit angiogenesis. The spectrum of effects on different elements of the PA system observed in response to the agents assessed suggests that the role of modulations in extracellular proteolytic activity in anti-angiogenesis is likely to be varied and complex.

Recombinant truncated thrombospondin-1 monomer modulates endothelial cell plasminogen activator inhibitor 1 accumulation and proliferation in vitro

The angiogenic and malignant phenotypes of hamster tumor cells are inversely correlated with the expression of an amino terminally truncated thrombospondin (TSP) subunit. In the present study, we have constructed a truncated TSP subunit from a human fibroblast cDNA library (rt-TSP1) and expressed it in Chinese hamster ovary (CHO) cells. Increased concentrations of plasminogen activator inhibitor-1 (PAI-1) were detected in endothelial cell conditioned medium following treatment with rt-TSP1. This rt-TSP1-induced increase in PAI-1 was neutralized by monoclonal antibodies to both TSP and TGF beta. rt-TSP1 also inhibits the proliferation of endothelial cells and this response is also neutralized by TSP and TGF beta antibodies. Serine and cysteine proteases inhibitors were used to determine if rt-TSP1 activated the latent TGF beta. However, these protease inhibitors did not neutralize the effect of rt-TSP1. The data indicate that the anti-angiogenic properties of TSP may be due to inhibition of the pericellular proteolysis required for endothelial cell migration and endothelial cell proliferation.

Visualization of histamine binding to nuclei

The binding of histamine to cultured microvascular endothelial cells and glycol methacrylate embedded ovarian tissue sections has been localized using fluorescein-albumin-histamine conjugate. Histamine conjugate was bound to the plasma membranes and nuclei of luteal, endothelial, and ovarian stromal cells. An apparent increase in the binding of histamine to nuclei was observed in the presence of cimetidine but the plasma membrane staining was still evident. Unlike cimetidine, pyrilamine completely inhibited the binding of histamine to the plasma membrane. Instead, in the presence of pyrilamine, histamine bound exclusively to the nuclei of endothelial, germinal epithelial, granulosa, and stromal cells. However, the nuclei of terminally differentiated luteal cells and oocytes were not labeled. The functional significance of these nuclear histamine binding sites remains to be determined.

Isolation and characterization of microvascular endothelial cells from developing corpus luteum

We have isolated and characterized microvascular endothelial cells from the developing rabbit corpus luteum. The isolated cells express Factor VIII-related antigen and angiotensin-converting enzyme, internalize acetylated low-density lipoprotein, and form capillary-like tubules in collagen gel cultures. Of the mitogens tested, only basic fibroblast growth factor stimulated the proliferation of these cells. Transforming growth factor-beta 1 and tumor necrosis factor-alpha strongly inhibited the proliferation of these endothelial cells. Platelet-derived growth factor, epidermal growth factor, insulin-like growth factor-1, histamine, prostaglandins, sex steroids, and interleukin-6 (interferon-beta 2) had no effect on the proliferation of these microvascular endothelial cells from the corpus luteum, whereas interleukin-1 alpha and 1 beta were mildly inhibitory. Endothelial cells are an essential component of corpus luteum physiology. Therefore, the availability of these cells will allow us to investigate the potential interactions between endothelial cells and luteal cells in vitro.

Specific inhibition of endothelial cell proliferation by thrombospondin

Angiogenesis is a multi-step event involving endothelial cell migration, attachment, and proliferation. A thrombospondin (TSP)-like protein has recently been described as a naturally-occurring inhibitor of angiogenesis. We now report that human platelet TSP inhibits the in vitro proliferation of endothelial cells from the rabbit corpus luteum, bovine adrenal cortex and pulmonary artery, and human umbilical vein. The antiproliferative effect of TSP was neutralized by monoclonal antibodies against TSP. The growth arrest seen with TSP was specific for endothelial cells since TSP actually stimulated the growth of vascular smooth muscle cells and human foreskin fibroblasts. These results imply that the angiogenesis-inhibiting effect of TSP is mediated through an inhibition of endothelial cell proliferation. Elucidation of the mechanism of action of TSP on endothelial cell proliferation may lead to potential therapeutic approaches for the control of neovascular diseases.

Aprotinin antagonizes the binding of human chorionic gonadotropin to its receptor

Aprotinin caused a dose-dependent inhibition of [125I]hCG binding to its receptor in plasma membranes prepared from luteinized rat ovaries. Displacement of [125I]hCG from its receptor by aprotinin was temperature dependent, with an ID50 of 300 microM at 4 C and an ID50 of 3700 microM at 22 C. Equilibrium binding data showed a decrease in the Ka for hCG in the presence of increasing concentrations of aprotinin; aprotinin had no effect on the number of binding sites. The rate of association of hCG with its receptor was markedly reduced in the presence of aprotinin, but aprotinin had little effect on the rate of dissociation. Control experiments established that aprotinin did not inhibit the binding of [125I]hCG to its receptor due to its lectin properties, an ionic effect or some irreversible impairment of the receptor or hormone. Aprotinin did not inhibit hCG binding when the receptor was solubilized out of ovarian membranes with Triton X-100. Aprotinin inhibited the hCG-mediated activation of adenylate cyclase in rat ovarian plasma membranes in a dose-dependent manner. Similarly, aprotinin antagonized the hCG-stimulated biosynthesis of progesterone by dispersed rat luteal cells. The maximal agonistic activity of hCG was attenuated in these two bioassays. The data are compatible with a hypothesis that aprotinin sterically hinders the entry of hCG into its receptor site by binding to a protease in the plasma membrane that is closely associated with the hCG receptor. This proposal is consistent with the emerging concept that integral membrane proteases are modulators of receptor function.

Inhibition of gonadotropin-stimulated adenylate cyclase by dansyl-arginyl-(4'-ethyl)piperidine amide (DAPA)

Protease inhibitors are known to suppress basal, fluoride-, and hormone-stimulated adenylate cyclase activities. The thrombin inhibitor, dansyl-arginyl-(4'-ethyl)piperidine amide (DAPA), also specifically inhibits the binding of gonadotropins to their receptors. Our studies were undertaken to find a concentration of DAPA that would specifically inhibit gonadotropin-stimulated adenylate cyclase without significantly altering basal, fluoride-, isoproterenol-, or prostaglandin E1-stimulated cyclase. Basal adenylate cyclase activity was not inhibited by DAPA in either human chorionic gonadotropin (hCG)- or follicle-stimulating hormone (FSH)-responsive rat ovarian plasma membranes. Human chorionic gonadotropin-stimulated cyclase was completely inhibited by DAPA at a concentration of 2.96 mM; the ID50 was 1.32 mM. Follicle-stimulating hormone-stimulated cyclase was completely inhibited by a DAPA concentration of 4.44 mM, and the ID50 was 1.75 mM. Dansyl-arginyl-(4'-ethyl)piperidine amide (2.96 mM) inhibited isoproterenol-, prostaglandin E1-, and fluoride-stimulated cyclase in hCG-responsive membranes by 11%, 28%, and 35%, respectively. Dansyl-arginyl-(4'-ethyl)piperidine amide (4.44 mM) inhibited fluoride- and prostaglandin-stimulated cyclase in FSH-responsive membranes by 10% and 11%, respectively. The data show that appropriate concentrations of DAPA can antagonize gonadotropin-stimulated adenylate cyclase while only minimally affecting fluoride- and other receptor-activated cyclase activities.

Secondary amenorrhoea and 47,XX,i(Xq) karyotype

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Relationship between progesterone receptor binding and progestin biological activity

The binding affinities of a series of steroidal compounds for the hamster uterine progesterone receptor were determined using two sets of incubation conditions. These competitive binding conditions were designed to deduce the relative rates of ligand dissociation from the progesterone receptor. The progestin activity of these compounds was also determined in a bioassay employing the measurement of diamine oxidase in the traumatized hamster uterus. Steroids could be classified into two categories based on either an increase or decrease in relative binding affinity (RBA) with increasing time of competitive incubation. The mean (+/- SEM) progestin biopotency for the compounds having an increase in RBA was 120 +/- 18 (progesterone = 100), while the biopotency for compounds having a decrease in RBA was only 44 +/- 17. This difference was significant (P less than 0.01). Linear regression analyses revealed significant correlations between the RBAs and progestin biopotencies. Compounds showing a decrease in RBA with increasing time of incubation did not have antiprogestin activity. Kinetic studies of this type should be useful for selecting compounds with potent agonistic activity, but cannot unequivocally predict antihormonal activity.

Additional studies on pregnancy termination and inhibition of the monkey corpus luteum with 5-oxa-17-phenyl-18,19,20-trinor-PGF1 alpha methyl ester and structurally related prostaglandins

Oral administration of 5-oxa-17-phenyl-18,19,20-trinor-PGF1 alpha methyl ester (PGF-analog) resulted in a consistent and dose-dependent inhibition of corpus luteum progesterone production in nonpregnant rhesus monkeys concomitantly treated with human chorionic gonadotropin. Similarly, vaginal suppositories containing PGF-analog also inhibited the monkey corpus luteum. Side effects by the oral route of administration were minimal, whereas side effects following vaginal treatment with PGF-analog were higher. Five prostaglandins with structural similarity to PGF-analog were studied for their ability to inhibit the monkey corpus luteum, but none showed an advantage over the parent molecule. PGF-analog did not synergize with 9-deoxo-16,16-dimethyl-9-methylene-PGE2 for the inhibition of the monkey corpus luteum, nor did it synergize with (15S)-15-methyl-PGF2 alpha methyl ester for the interruption of early pregnancy in the monkey. 9-Deoxo-9-methylene-5-oxa-17-phenyl-18,19-20-trinor-PGE1 methyl ester did not terminate early gestation in the monkey at doses of 8 or 24 mg.

Biologic activity of human chorionic gonadotropin following reversed-phase high-performance liquid chromatography

Human chorionic gonadotropin (hCG) was analyzed by reversed-phase high-performance liquid chromatography (HPLC) using mobile phases previously described in the literature, as well as newly developed solvent systems. Fractions of hCG collected following reversed-phase HPLC were bioassayed by activation of adenylate cyclase to determine their biologic potencies. hCG retained only 10-60% of its biologic activity following reversed-phase HPLC, depending on the chromatographic conditions employed. A portion of the reduced biologic activity was attributed to dissociation of the alpha- and beta-subunits of hCG at the low pH of the mobile phases, since neutralization of the pH prior to lyophilization and bioassay increased the biologic potency of the chromatographed hormone. The remaining loss in biologic activity is presumably due to organic solvent denaturation.

Inhibition of folliculogenesis in the monkey following early follicular phase administration of an LRH agonist

This study was undertaken to determine if early follicular phase administration of a synthetic luteinizing hormone releasing hormone (LRH) agonist would produce luteal phase defects in the monkey. [D-His(im-Bzl)6,Pro9]LRH N-ethylamide was administered to groups of rhesus monkeys on days 1-3 of the menstrual cycle. Two responses were observed: a) anovulatory menstrual cycles of less than 14 days duration, and b) ovulatory menstrual cycles characterized by unusually long follicular phases. All 4 monkeys with shortened menstrual cycles had prominent increases in serum gonadotrophin and oestradiol concentrations during treatment with the LRH agonist; early menses in these animals was attributed to uterine bleeding upon oestrogen withdrawal. Serum FSH concentrations declined, serum LH concentrations were unaltered, and only 2 of 8 monkeys had elevations in serum oestradiol during ovulatory menstrual cycles. The mean interval from cessation of treatment with the LRH agonist to the next preovulatory gonadotrophin surge was 21.5 +/- 3.2 days in ovulatory menstrual cycles. Corpus luteum function was normal following treatment with the LRH agonist in ovulatory cycles. The results indicate that both the long and short menstrual cycles observed following early follicular phase administration of the LRH agonist to monkeys can be attributed to a profound inhibition in follicle recruitment. [D-His(im-Bzl)6,Pro9]LRH N-ethylamide did not alter corpus luteum function in the monkeys.

Interruption of early pregnancy in the monkey with mestranol and 5-oxa-17-phenyl-18,19,20-trinor prostaglandin F1 alpha methyl ester

Prior work has shown that 5-oxa-17-phenyl-18,19,20- trinor prostaglandin F1 alpha methyl ester (PGF-analog) inhibits luteal progesterone secretion, but does not shorten menstrual cycles in human chorionic gonadotropin (hCG)-treated, nonpregnant monkeys. This report demonstrates that a combination treatment of PGF-analog and mestranol not only reduces blood progesterone concentrations in the hCG-treated monkey, but also results in a significant shortening of menstrual cycles. The corpus luteum-inhibiting activity of PGF-analog in hCG-treated, nonpregnant monkeys was not enhanced by simultaneous administration of nonestrogenic steroids (norethisterone, oxymetholone, azastene , 17 alpha-allyl-3-methoxy-1,3,5(10)- estratrien-17 beta-ol). Most importantly, pregnancy was interrupted in 11 or 12 monkeys when PGF-analog and mestranol were administered on Day 28 of fertile menstrual cycles; this abortifacient activity of the prostaglandin-estrogen treatment was not prevented by concomitant administration of progesterone. Administration of PGF-analog and mestranol in the third trimester terminated pregnancy in only 1 of 3 monkeys. The data indicate that a combination treatment of PGF-analog and mestranol is highly effective for the termination of early pregnancy in the monkey. Although PGF-analog and mestranol clearly inhibit the monkey corpus luteum, it is unlikely that this activity is essential for the abortifacient activity of the prostaglandin-estrogen treatment.

Inhibition of the primate ovarian cycle by a porcine follicular fluid protein(s)

Monkeys received twice daily intramuscular injections of 3 mg of purified porcine follicular fluid protein(s) for the first 14.5 days of the menstrual cycle. Two of five treated monkeys had anovulatory menstrual cycles. Three monkeys had cycles characterized by long follicular phases, low follicular and luteal phase serum estradiol concentrations, and subnormal luteal progesterone production. Serum gonadotropin concentrations were not affected by the follicular fluid protein(s). The data demonstrate in the nonhuman primate that porcine follicular fluid contains a protein(s) that acts at the ovarian level to inhibit gonadotropin action.

Arrest of folliculogenesis and inhibition of ovulation in the monkey following weekly administration of progestins

Studies were undertaken in the rhesus monkey to determine whether development of a dominant ovarian follicle could be repeatedly arrested by the administration of a progestin on day 7 of the menstrual cycle, and then every 7 days thereafter regardless of menstrual bleeding history. Progesterone (7.5 mg), norethisterone (1.5 mg), and 17 alpha-ethinyl-17 beta-methoxy-7 alpha-methyl-4-estren-3-one (1.0 or 1.5 mg) effectively inhibited ovulation when injected intramuscularly once a week for 8 weeks. Orally administered STS 557 (17 alpha-cyanomethyl-17 beta-hydroxy-4,9-estradien-3-one, 1.0 mg) also inhibited ovulation. Two structurally related steroids (17 beta-methoxy-4-estren-3-one, 1.0 mg; and 17 beta-methoxy-7 alpha-methyl-4-estren-3-one, 1.5 mg) did not inhibit ovulation when given intramuscularly at the indicated doses. Although weekly administration of certain progestins effectively arrested follicular development and inhibited ovulation in the primate, the treatment was accompanied by disturbances in menstrual bleeding patterns.

Pregnancy interception with a combination of prostaglandins: studies in monkeys

Treatment with combinations of synthetic prostaglandins, one with an ovarian site of action and one with a uterine site of action, terminated pregnancy in all rhesus monkeys given the injection on day 28 of fertile menstrual cycles. Single prostaglandins, even at higher doses, interrupted pregnancy in only one-third of the monkeys. The most effective treatment, 5-oxa-17-phenyl-18,19,20-trinor prostaglandin F1 alpha methyl ester plus 9-deoxo-16,16-dimethyl-9-methylene prostaglandin E2, promptly intercepted early pregnancy after a single administration and without side effects.

The effect of oxytocin on the corpus luteum of the monkey

The effect of a pharmacologic dose of synthetic oxytocin on corpus luteum function was evaluated in rhesus monkeys during normal menstrual cycles, or during menstrual cycles in which the corpus luteum was concomitantly stimulated by injections of human chorionic gonadotropin (hCG). Oxytocin administered by intramuscular injection at a total dose of 4.5 milligrams (2250 I.U.) on Day +6 of the normal luteal phase (Day 0 is the day of the midcycle LH surge) did not change the concentrations of progesterone in the peripheral serum of monkeys or alter the duration of the luteal phase. The same dose of oxytocin, administered to monkeys on Day 22 of menstrual cycles in which hCG was also given on Days 20-22, caused a small, but statistically significant, reduction in serum progesterone values. The results indicate that oxytocin does not alter luteal life span or markedly change blood progesterone concentrations in primates.

Synthesis and biological activity of prostaglandin lactones

Most of the primary prostaglandins and several biologically important prostaglandin analogues were converted to 1,9-, 1,11- or 1,15-lactones, in order to investigate the biological profiles of these internal esters and to assess their potential as prodrugs for the corresponding open-chain hydroxy acids. In each case, the key lactonization step was done using Corey's "double activation" procedure (cyclization of omega-hydroxy-2-pyridinethiol esters). In general, the 1,9-lactones exhibited less than 1% of the biological activity of the parent hydroxy acids in the standard prostaglandin test systems. The 1,11- and 1,15-lactones, on the other hand, were essentially equal to the parent hydroxy acids as antifertility agents (a 4-day assay which would allow time for in vivo enzymatic lactone hydrolysis). The 1,11- and 1,15-lactones exhibited very low activity in acute or in vitro screens (e.g., rat blood pressure and gerbil colon stimulation), assays which more closely reflect the intrinsic activity of the lactones themselves. These results are consistent with the observed relative ease of enzymatic hydrolysis of the prostaglandin lactones (1,15 greater than or equal to 1,11 much greater than 1,9). Several of the lactones whose parent hydroxy acids are resistant to metabolic inactivation (e.g., 15-methyl, 16-phenoxy, and 17-phenyl) exhibited potent abortifacient activity in the hamster. These lactones, with greatly diminished activity in the blood pressure and smooth muscle assays (indicators of potential side effects), represent a therapeutically useful class of antifertility agents.

Steroidogenic responsiveness of the monkey corpus luteum to exogenous chorionic gonadotropin

Groups of female rhesus monkeys were given a 5-day regimen of im injections of hCG (30, 60, 90, 180, and 360 IU, respectively) beginning 2, 6, 10, or 14 days after the midcycle LH surge (day 0). Serum progesterone concentrations in the day 2 treatment group did not differ markedly from values observed in control monkeys throughout normal menstrual cycles. In contrast, monkeys receiving hCG beginning on days 6, 10 or 14 had immediate significant increases in serum progesterone in response to the first injection of hCG. Dramatic responses were seen in the day 6 and 10 groups (2.5- and 5-fold elevations in serum progesterone, respectively); progesterone values plateaued at about 13 ng/ml during the hCG treatment interval. Monkeys receiving hCG on day 14 had 4-fold elevations in serum progesterone, but concentrations did not exceed 6 ng/ml. Serum estradiol increased significantly after hCG to concentrations between 200-300 pg/ml in all treatment groups; peak values were seen at the time of or in the days immediately after the last hCG injection. Serum testosterone concentrations were not significantly altered by hCG administration at any stage of the luteal phase. hCG did not sustain serum steroid hormone concentrations in monkeys with the corpus luteum removed on day 10 of the luteal phase. A 10-day regimen of increasing hCG doses beginning on day 10 of the luteal phase mimicked the steroid hormone secretion patterns observed in control monkeys during early pregnancy. The data show that the qualitative and quantitative steroidogenic capacities of monkey corpora lutea after a gonadotropin challenge are profoundly affected by luteal age.

Synthesis of [1, 6-cyclo (acetyl-1-L-glutamic acid, 2-D-phenylalanine, 3-D-tryptophan, 6-D-lysine)] luteinizing hormone-releasing hormone on poly-N-acrylylpyrrolidine resin

The protected peptide, Ac-Glu(OBut)-D-Phe-D-Trp-Ser(But)-Tyr(But)-D-Lys (Z)-Leu-Arg(Tos)-Pro-Gly-NH2 was synthesized in a stepwise manner on a resin of poly-N-acrylylpyrrolidine using both acid cleavable N alpha-tert.-butyloxycarbonyl and base cleavable N alpha-fluorenylmethyloxycarbonyl protecting groups. After cleavage by ammonolysis in methanol, the tert.-butyl and benzyloxy-carbonyl side-chain protecting groups were cleaved with CF3-CO2H-thioanisole and the 1-6 amide ring formed by cyclization with diphenylphosphorylazide, after which the remaining tosyl protecting group was cleaved in HF-anisole. [1,6-Cyclo(Ac-Glu1, D-Phe2, D-Trp3, D-Lys6]LH-RH exhibited less than 10% of the antiovulatory potency of [D less than Glu1, D-Phe2, D-Trp3,6] LH-RH, a potent linear antagonist.

Comparison of three subcutaneous modes of prostaglandin F2 alpha administration for pregnancy termination in the hamster

Dose response relationships for pregnancy termination in hamsters following administration of prostaglandin F2 alpha (PGF2 alpha) by three subcutaneous methods were determined in 526 hamsters. The median effective dose (ED50) for PGF2 alpha given as a single subcutaneous injection in 500 microliters of saline was 22.2 micrograms. Administration of the prostaglandin with an Alzet osmotic minipump (subcutaneous insertion for 24 hours) required 1.35 times more PGF2 alpha (ED50=30.0 micrograms). The least effective method of pregnancy termination in the hamster involved administration of PGF2 alpha by a single subcutaneous injection in 20.4 microliters of saline (the same volume delivered by the minipump in 24 hours); the ED50 for this method of administration was 41.3 micrograms of PGF2 alpha.

Persistence of progesterone secretion after foetal death induced by vasopressin in rabbits

Synthetic lysine-vasopressin (2 IU/kg body weight) terminated pregnancy in the rabbit when administered im on day 20, but not when administered on days 8 through 11 of gestation. Rabbits treated with vasopressin on day 20 delivered necrotic foetuses at the expected time of parturition (13/19 animals, day 32), aborted (3/19), or resorbed their foetuses (3/19). Uterine bleeding was noted in 68% of rabbits 5 days after vasopressin treatment on day 20 of pregnancy. Plasma concentrations of progesterone in vasopressin and saline treated rabbits were identical throughout pregnancy. Placental engorgement by erythrocytes was associated with foetal death in rabbits 1 h after vasopressin treatment on day 28 of gestation. Although vasopressin administration during the last third of gestation is detrimental to foetal life in the rabbit, the continuing normal secretion of progesterone indicates that the placentas remain viable. Available evidence suggests that foetal death results from ischaemia caused by placental vascular congestion and stasis following vasopressin administration.

Inhibition of the monkey corpus luteum with 15-methyl prostaglandins

The corpus luteum inhibiting properties of eighteen 15-methyl prostaglandin analogs were determined in the rhesus monkey during concomitant stimulation of the corpus luteum with chorionic gonadotropin. The methyl ester of (15S)-15-methyl PGF2 alpha (15M-PGF2 alpha, 12.5 mg/monkey) lowered serum progesterone to 12% of pretreatment values within 24 hours, however progesterone returned to normal limits within 48 hours. Elongation of the top side-chain by two carbons (2a,2b-dihomo-15M-PGF2 alpha methyl ester, 13 mg/monkey), substitution of a hydroxymethyl group at carbon 1 (2-decarboxy-2-hydroxymethyl-15M-PGF2 alpha, 12 mg/monkey), or the formation of the carbon 1 amide (15M-PGF2 alpha amide, 12.5 mg/monkey) improved the inhibitory activity of 15M-PGF2 alpha; serum progesterone for these 3 analogs was depressed to 15-30% of pretreatment levels within 24 hours, and did not return to control values. Luteal function was not inhibited (12 or more mg/monkey) when the 15-methyl group was placed in the R configuration, the top side chain was shortened by two carbons, an amino group was substituted for carbon 1, the 5-oxa modification was added, or the 1,9-lactone was formed. Some other modifications of 15M-PGF2 alpha were also inactive, although not all were tested at equivalent doses: 2,2-difluoro; 4,5-cis-didehydro; 9,11-dideoxy-9 alpha, 11 alpha-dichloro; 11-deoxy; 17-phenyl; 1,15-lactone; and the p-benzamidophenyl ester of 2a,2b-dihomo-15M-PGF2 alpha. (15S)-15-Methyl PGE2 methyl ester (1 mg/monkey) depressed serum progesterone concentrations to 42% of pretreatment values within 24 hours; 2a,2b-dihomo-11-deoxy-(15S)-15-methyl PGE2 methyl ester was inactive (5 mg/monkey). A corpus luteum inhibiting action of certain 15-methyl prostaglandins can be demonstrated in the rhesus monkey.

Effects of (15S)-15-methyl prostaglandin E2 alpha methyl ester and estrogens upon the corpus luteum and conceptus of the rhesus monkey

The corpus luteum inhibiting activity of (15S)-15-methyl prostaglandin F2 alpha methyl ester (15M-PGF2 alpha) was determined when given in combination with estrogens. Administration of 15M-PGF2 alpha alone (3 injections of 500 microgram each) to monkeys concomitantly receiving hCG reduced serum progesterone concentrations to 50% of values observed in control animals. Ethinyl estradiol or mestranol alone did not inhibit the corpus luteum of the hCG-treated, nonpregnant monkey. Serum progesterone values for nonpregnant monkeys treated with 15M-PGF2 alpha plus estradiol-17 beta, ethinyl estradiol or mestranol did not differ statistically from those observed in monkeys treated with 15M-PGF2 alpha alone. The dose of 15M-PGF2 alpha (3 x 500 microgram) which only partially inhibited the corpus luteum of the hCG-treated, nonpregnant monkey promptly terminated gestation when given on Day 28 od fertile menstrual cycles. Pregnancy terminated in two of three treated monkeys when the dose of 15M-PGF2 alpha was reduced ten-fold (3 x 50 microgram). Mestranol alone reduced serum progesterone and estradiol-17 beta concentrations to one-half and one-third of pretreatment values, but did not interrupt pregnancy. Pregnancy terminated in only two of five monkeys when mestranol was administered with the low dose of 15M-PGF2 alpha. It is concluded that: 1) estrogens do not enhance the corpus luteum inhibiting of 15M-PGF2 alpha in the nonpregnant monkey; 2) the primary action of 15M-PGF2 alpha during early pregnancy is upon the conceptus and not the corpus luteum; 3) concomitant treatment with mestranol and 15M-PGF2 alpha offers no advantage of 15M-PGF2 alpha alone for the termination of early pregnancy; and 4) mestranol alone can impair the steroidogenic potential of the corpus luteum of early pregnancy, but is not sufficiently active to terminate gestation.

Inhibition of preovulatory gonadotropin secretion in the rhesus monkey by [(<Glu-Pro)1,D-Phe2,D-Trp3,6]-LHRH

We report the first example of a complete inhibition of preovulatory gonadotropin secretion resulting from administration of a luteinizing hormone releasing hormone antagonist during a spontaneous menstrual cycle. The antagonist, [(<Glu-Pro)1,D-Phe2,D-Trp3,6]-LHRH, was administered to a rhesus monkey beginning on Day 9 of the menstrual cycle; ovulation did not occur and preovulatory peaks of LH and FSH were not observed despite elevations in serum estradiol-17 beta of sufficient strength and duration to elicit gonadotropin surges. Midcycle gonadotropin surges had already commenced in another monkey, however the antagonist did partially inhibit LH and FSH secretion although ovulation and luteinization were not prevented. Normal hormone secretion patterns and luteal function were observed in another monkey when the antagonist was given after the midcycle FSH and LH peaks had already occurred. These data emphasize the importance of beginning treatment with LHRH antagonists early in the follicular phase of the menstrual cycle.

Periovulatory endocrine events in the stumptailed monkey (macaca arctoides)

Blood samples were obtained frequently from stumptailed monkeys (Macaca arctoides) at midcycle and assayed for FSH, LH, 17 beta-estradiol, and progesterone. Periovulatory endocrine events were generally similar to those which have been described in rhesus monkeys and women. Although the midcycle patterns of estradiol in individual monkeys appeared quite varied, careful evaluation indicated the following general characteristics: 1) a plateau or transient decline in estradiol 30-44 h before the LH peak, 2) a sharp rise in serum estradiol before the initiation of the LH rise, 3) a diminution in serum concentrations or a decline in the rate of estradiol increase at the initiation of the LH rise, and 4) an elevation in estradiol at the time of the highest serum LH value. The first elevation in serum progesterone occurred 0-12 h before the LH peak and after the initiation of the LH surge. An unusual finding was a second midcycle rise in serum FSH, which occurred 2-3 days after the LH peak in 10 of 13 menstrual cycles. The biological significance of this second FSH rise in stumptailed monkeys is not known with certainty, but available evidence suggests that it enhances postovulatory progesterone and estrogen syntheses. Two methods are presented for the RIA of serum FSH in the stumptailed macaque.

Steroid binding specificity of the hamster uterine progesterone receptor

The relative binding affinities (RBA) of 51 steroids were determined for the uterine progesterone receptor of the proestrous hamster. The receptor demonstrated a high specificity for progesterone; most structural modifications to the progesterone molecule resulted in a substantial reduction in binding affinity. Only six steroids had relative binding affinities similar to progesterone (RBA=100): 17 alpha-ethinyl-17 beta-methoxy-4-androsten-3-one (RBA=85); 6 alpha-fluoro-4-pregnene-3,20-dione (RBA=94); 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (RBA=96); 19-nor-4-pregnene-3,20-dione (RBA=110); 21-fluoro-4-pregnene-3,20-dione (RBA=119); and 17 alpha-ethinyl-17 beta-methoxy-4-estren-3-one (RBA=123).

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection

Adult male rhesus were treated with PGE2, PGF2 alpha or the 13,14-dihydro-15-keto metabolite of PGE2 in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF2 alpha was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE2 was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE2 or PGF2 alpha can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.

Characterization of the exfoliative antispermatogenic agent 1-(2,4-dichlorobenzyl)-H-indazole-3-carboxylic acid in the rhesus monkey

The effects of oral doses of 1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid (DICA) on spermatogenesis in the rhesus monkey (Macaca mulatta) was studied. Four animals given five daily 50 mg/kg doses or three or five daily 500 mg/kg doses showed that DICA was an exfoliating antispermatogenic compound. The inhibition of spermatogenesis was only partially reversible following 500 mg/kg doses of DICA. Weekly and monthly 50 mg/kg doses of DICA only partially inhibiting spermatogenesis as measured by electro-ejaculated sperm counts. Response in individual monkeys ranged from azoospermia to no effect. Testicular biopsies confirmed this finding. DICA did not affect serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), or testosterone concentrations. The blood absorption or urinary excretion rates of uniformly tritiated DICA in the animals that responded well did not differ from those monkeys that responded poorly. DICA metabolites were not detected in monkey urine. Serum testosterone concentrations appeared to vary with the season of the year, but FSH concentrations and ejaculated sperm count did not.

Luteolytic action of 15-keto prostaglandin F2alpha in the rhesus monkey

The naturally-occurring metabolite of prostaglandin F2alpha, 15-keto prostaglandin F2alpha (15-keto PGF2alpha), elicited rapid and sustained declines in serum progesterone concentrations when administered to rhesus monkeys beginning on day 22 of normal menstrual cycles. Evidence for luteolysis of a more convincing nature was obtained in studies where a single dose of 15-keto PGF2alpha was given on day 20 of ovulatory menstrual cycles in which intramuscular injections of hCG were also given on days 18-20; serum progesterone concentrations fell precipitously in monkeys within 24 hours following intramuscular administration of 15-keto PGF2alpha. However, corpus luteum function was impaired in only 4 of 11 early pregnant monkeys when 15-keto PGF2alpha was administered on days 30 and 31 from the last menses, a time when the ovary is essential for the maintenance of pregnancy. Gestation failed in 2 additional monkeys 32 and 60 days after treatment with 15-keto PGF2alpha, but progressed in an apparently normal manner in the remaining 5 animals. Two pregnant monkeys treated with 15-keto PGF2alpha on day 42 from the last menstrual period, a time when the ovary is no longer required for gestation, continued their pregnancies uneventfully. Corpus luteum function was not impaired in 9 control monkeys which received injections of vehicle or hCG at appropriate times during the menstrual cycle or pregnancy.

Luteal phase defects in the rhesus monkey: the significance of serum FSH:LH ratios

Luteal phases of an abbreviated duration or suboptimal progesterone secretion were identified in the rhesus monkey. Characterization of menstrual cycles with short luteal phases (8 days) in 5 monkeys revealed the following deviations from normal: a. a failure of serum FSH to decline progressively from an early follicular phase high to a preovulatory nadir; b. a commonly inadequate, or absent, preovulatory FSH surge; c. subnormal serum LH concentrations during both the follicular and luteal portions of the menstrual cycle; d. ratios of serum FSH:LH which did not progressively decrease during the follicular phase; and e. serum estradiol concentrations below normal values during the luteal portion of the menstrual cycle. One monkey had abnormally low serum concentrations of progesterone, although the luteal phase was 19 days in duration. Serum gonadotropin and estradiol patterns in this latter monkey were identical to those observed in monkeys with short luteal phases. It is concluded that inappropriate ratios of serum FSH:LH during the follicular phase of the menstrual cycle result in impaired corpus leteum function. The data document the usefulness of the nonhuman primate for investigating those luteal phase defects which also occur in the woman.

A new radioimmunoassay for follicle-stimulating hormone in macaques: ovulatory menstrual cycles

A sensitive and specific radioimmunoassay system for macaque follicle-stimulating hormone (mFSH) was developed utilizing an antiserum (H-31) prepared in a rabbit against purified ovine FSH as the immunogen. Sera from castrated female, adult male, and juvenile rhesus monkeys, as well as urinary extracts from castrated rhesus and bonnet monkeys, were used to demonstrate parallelism with a standard of partially purified monkey pituitary gonadotropins (LER-M-907-D). An extract of baboon pituitary tissue also showed parallelism with the reference standard. A highly purified pituitary extract (WP-X-105-28), containing approximately 75% macaque luteinizing hormone (mLH) and 1% mFSH, was used to demonstrate the specificity of this mFSH assay system. Sera and urinary extracts obtained from hypophysectomized monkeys did not show cross-reactivity in the assay. Macaque chorionic gonadotropin (mCG) did not produce an inhibition curve in the assay, as determined from serum samples and urinary extracts collected from pregnant monkeys at the time of peak mCG secretion. Serum concentrations of mFSH were suppressed in ovariectomized monkeys by the administration of ethinyl estradiol for 3 days, but returned to near pretreatment values by 96 h after the last estradiol administration. The determination of serum mFSH concentrations in daily blood samples obtained from 20 rhesus monkeys throughout ovulatory menstrual cycles revealed a pattern similar to that previously reported for the rhesus monkey and the woman. The peak value of serum mFSH during the menstrual cycle coincided with the midcycle surge of mLH in each case. The gonadotropin peaks were preceded by increasing serum concentrations of estradiol and followed by rises in the serum concentrations of progesterone. The follicular phase of the menstrual cycle was characterized by continuously decreasing serum concentrations of mFSH, reaching a preovulatory nadir 48 h prior to the midcycle mFSH and mLH surges. Serum mFSH concentrations following the midcycle gonadotropin surges decreased progressively as serum progesterone concentrations increased and reached a plateau, and then increased during the last week of the menstrual cycle as corpus luteum function was waning. We have prepared a large pool of antiserum for distribution under the aegis of the Contraceptive Development Branch of the Center for Population Research, the National Institute of Child Health and Human Development.

Peripheral plasma progesterone during egg transport in the rabbit

Peripheral plasma progesterone concentrations were measured in New Zealand rabbits every 6 hr beginning 12 hr before and continuing until 96 hr after either natural mating, hCG injection, or saline injection. The number of ovulation points in naturally mated animals (9.3 +/- 0.6, mean +/- SE) was not significantly different from that in hCG-injected animals (8.6 +/- 1.5). There was a surge in progesterone secretion following both mating and hCG injection. Plasma progesterone concentrations reached a peak prior to ovulation and then fell to basal levels at the time of ovulation. Beginning at approximately 30 hr after the ovulation-inducing stimulus, there was a progressive, significant (P less than 0.001) increase in plasma progesterone concentration, which continued for the duration of the sampling period. The initiation of the postovulatory increase in progesterone secretion corresponds temporally with the movement of eggs from the ampullary-isthmic junction into the isthmus. The progressive increase in plasma progesterone between 30 and 72 hr after the induction of ovulation corresponds with the gradual movement of eggs through the isthmus into the uterus. The data suggest that movement of eggs through the oviductal isthmus is influenced by the postovulatory secretion of progesterone.

Prostaglandin F2alpha and human prostatic affinity for testosterone

Earlier work had shown that the lactogen, LTH and HPL, foster testosterone binding by the prostate. This study was undertaken to see if prostaglandin F2alpha would oppose the effect of the lactogen on the prostate as it does the luteotrophic action of the hormone on the corpus luteum. When it was found instead that the PGF increases steroid binding and that its interaction with lactogen was neither antagonistic nor additive, attention was directed to further characterization of prostaglandin's effect. A dosage/response study of F2alpha alone showed that concentrations of 4 ng/ml and 40 ng/ml increased binding but that 400 ng/ml did not. Glands with stromal hyperplasia and/or inflammation were not responsive than those with epithelial hyperplasia. Assays of water extracts of the tissue revealed concentrations of about 340 ng of F2alpha per gram fresh weight and that the concentration varied inversely as the beta-glucuronidase activity. If the enzyme level is considered an index of the epithelial cell density within the specimen, the inverse relationship suggest a non-epithelial (stromal) site of prostaglandin concentration.