Harold Goldenberg

Effect of cyclic nucleotides on activity of cyclic 3′,5′-adenosine monophosphate phosphodiesterase

Abstract A series of cyclic 2′,3′-nucleotides, cyclic 3′,5′-nucleotides and derivatives of cyclic 3′,5′-adenosine monophosphate (cyclic AMP) with a substituent at the C-8 position were investigated as inhibitors of partially purified cyclic AMP phosphodiesterases (PDE) of cat heart and rat brain. The assays were carried out at a substrate concentration (0.06 μM) where the contribution to the total enzyme activity by phosphodiesterases with K m values for cyclic AMP above 100 μM was insignificant; consequently the activity measured was that of low K m enzymes. Cyclic 3′,5′-guanosine monophosphate (cyclic GMP) and cyclic 3′,5′-inosine monophosphate (cyclic IMP) were shown to be the most potent inhibitors of PDE of cat heart (I 50 = 1 and 2 μ M, respectively). Of the cyclic AMP derivatives tested that have a substituent at the C-8 position, 8-bromo cyclic AMP was the most potent inhibitor; next most potent were the derivatives with a sulfur atom, whereas derivatives with oxygen- or nitrogen-containing substituents were the least potent inhibitors of PDE of cat heart or rat brain. Most of the cyclic nucleotides that were tested were more potent inhibitors of the PDE of cat heart than that of PDE of rat brain. The kinetic properties of PDE of cat heart were also investigated in the presence of cyclic GMP, cyclic IMP and 8-bromocyclic AMP. All three compounds were found to be competitive inhibitors, with apparent K i values of 0.51, 2.3 and 20 μM respectively. The possible pharmacologic role of cyclic nucleotides is discussed.

Effects of SQ 14,225, an orally active inhibitor of angiotensin-converting enzyme on blood pressure, heart rate and plasma renin activity of conscious normotensive dogs.

Oral administration of SQ 14,225 (0.03--3 mg/kg) to conscious normotensive dogs caused inhibition of the pressor response to intravenously administered angiotensin I (AI), the duration of which was dose-dependent. All doses of 0.1 mg/kg or greater caused 85--95% inhibition 30 min after administration whereas 0.03 mg/kg produced only a 25% inhibition. Pressor responses to angiotensin II (AII) were not similarly inhibited. Blood pressure was moderately reduced in a dose-related manner and followed the same pattern as inhibition of the AI pressor responses. The maximum change occurred after 1.0 mg/kg with only a more rapid onset occurring after the 3.0 mg/kg dose. Heart rate was not appreciably changed. SQ 14,225 also increased plasma renin activity (PRA), the levels and duration of which were dose-related. These data indicate that SQ 14,225 is an orally effective, potent inhibitor of angiotensin I-converting enzyme (ACE) in dogs. It appears that in mongrel dogs, ACE inhibition results in a slight to moderate reduction in blood pressure and an increase in PRA.

The Effects of Captopril, Propranolol, and Indomethacin on Blood Pressure and Plasma Renin Activity in Spontaneously Hypertensive and Normotensive Rats

Summary Captopril reduced blood pressure and increased PRA in both SHR and NTR. Both propranolol and indomethacin caused significant reductions in resting PRA of both SHR and NTR but only propranolol caused an inhibition of the PRA changes caused by captopril. Furthermore, since propranolol was highly effective only in SHR and captopril decreased blood pressure much more in SHR than NTR, the increase in PRA caused by captopril in SHR was probably reflexly mediated by compensatory sympathetic activation, all of which actions were a consequence of reducing angiotensin II formation.

9α-homo-9,11-epoxy-5,13-prostadienoic acid analogues: Specific stable agonist (SQ 26,538) and antagonist (SQ 26,536) of the human platelet thromboxane receptor

A newly synthesized 9 alpha-homo-9,11-epoxy-5,13-prostadienoic acid analogue, SQ 26, 536, (8(R)9(S)11(R)12(S)-9 alpha-homo-9,11-epoxy-5(Z), 13(E)-15S-hydroxyprostadienoic acid) inhibited arachidonic acid (AA)-induced platelet aggregation with an I50 value of 1.7 microM. SQ 26,536 did not inhibit prostaglandin (PG) synthetase activity of bovine seminal vesicle microsomes or thromboxane (Tx) synthetase activity of lysed human blood platelets. SQ 26,536 also inhibited platelet aggregation induced by epinephrine (secondary phase), 9,11-azoPGH2 and collagen but did not inhibit the primary phase of epinephrine-induced aggregation or ADP-induced platelet aggregation. SQ 26,538 (8(R)9(S)11(R)12(S)-9 alpha-homo-9,11-epoxy-5(Z),13(E)-15R-hydroxyprostadienoic acid), a 15-epimer of SQ 26,536, induced platelet aggregation with an A50 value of 2.5 microM. SQ 26,536 competitively inhibited SQ 26,538-induced platelet aggregation with a Ki value of 3 microM. Neither indomethacin, a PG synthetase inhibitor, nor SQ 80,338 (1-(3-phenyl-2-propenyl)-1H-imidazole), a Tx synthetase inhibitor, inhibited SQ 26,538- or 9,11-azoPGH2-induced platelet aggregation. These data indicate that SQ 26,536 and SQ 26,538 are stable antagonist and agonist, respectively, of the human blood platelet thromboxane receptor.

Effects of SQ 27,427, a thromboxane A2 receptor antagonist, in the human platelet and isolated smooth muscle

The TxA2 receptor antagonist properties of SQ 27,427 [a cyclohexylcarbinol-7-oxabicyclo(2.2.1)heptenoic acid analog] were studied in vitro both in the human platelet and various isolated smooth muscle preparations. SQ 27,427 was found to be a potent inhibitor of human platelet aggregation induced by arachidonic acid, ADP, epinephrine, collagen and the stable TxA2 agonists 9,11-azoPGH2 and SQ 26,655. Inhibition of platelet aggregation was achieved at concentrations of SQ 27,427 which did not alter TxB2 levels. SQ 27,427 was found to weakly inhibit the formation of TxB2 from arachidonic acid and had no effect on the synthesis of PGE2 or PGI2 from arachidonic acid. SQ 27,427 was also found to be a weak stimulator of platelet adenylate cyclase, being 1000 times less potent than PGI2. In isolated smooth muscle experiments, SQ 27,427 was shown to be a potent and specific TxA2 receptor antagonist. It caused competitive antagonism of 9,11-azoPGH2-induced contractions of vascular, respiratory and gastrointestinal smooth muscles. This antagonism was specific, as responses to norepinephrine, serotonin, PGE2, PGI2, PGF2 alpha, histamine, carbachol and KCl were not altered by SQ 27,427.

Some Biochemical Characteristics of Human Breast Cancer and Nonmalignant Breast Lesions

Summary Human infiltrating ductal carcinoma of the breast, fibrocystic disease of the breast, and normal human mammary tissues were assayed for their concentration of nucleic acid, lipids, and 11 selected enzymes involved in carbohydrate, lipid, and amino acid metabolism. Comparing infiltrating ductal carcinomas to normal mammary tissue, striking elevations (p <0.001) were seen in pyruvate kinase (100-fold), glucose-6-phosphate, isocitrate and malate dehydrogenases (10-15-fold), free fatty acids and cholesterol (2-3-fold). The RNA/DNA ratios in the carcinomas were unchanged but triglycerides and α-glycerolphosphate dehydrogenase were reduced. Also studied were samples from eight cases of fibrocystic disease, a common nonmalignant proliferative disease of the human breast. Ranking the levels of nucleic acids and lipids and the activities of the enzymes in the tissues studied clearly showed that normal ≦ fibrocystic disease ≦ infiltrating ductal carcinoma. No significant differences in the biochemical characteristics of the carcinomas were found relative to the size of the lesion or to the menopausal state of the patient. These data on infiltrating ductal carcinomas closely resemble the data obtained from single dose 7,12-dimethylbenz [a] anthracene-induced rat mammary carcinomas, suggesting that the latter experimental tumor may represent a valid metabolic model of human breast cancer.

Some biochemical activities of 10,10-Difluoro-13-dehydroprostacyclin, a chemically stable analog of prostacyclin, in human blood platelets

Abstract 10,10-Difluoro-13-dehydroprostacyclin (DF 2 -PGI 2 ) is a chemically stable analog of prostacyclin (PGI 2 ). DF 2 -PGI 2 was 6 times more potent than prostaglandin E 1 (PGE 1 ), and 1/10 as potent as PGI 2 as an inhibitor of arachidonic acid (AA)-induced platelet aggregation. DF 2 -PGI 2 also inhibited platelet aggregation induced by collagen, ADP, epinephrine and two thromboxane agonists, 9,11-azoPGH 2 and SQ 24,810 (9,11-epoxy-9α-homo-5(Z), 13(E)-15β-hydroxyprostadienoic acid, racemic mixture). The antiaggregatory effects by DF 2 -PGI 2 and PGI 2 on AA-induced platelet aggregation were potentiated by etazolate (SQ 20,009), a potent inhibitor of cyclic AMP phosphodiesterase (PDE), and were blocked by SQ 22,536 (9-(tetrahydro-2-furyl) adenine), an inhibitor of adenylate cyclase (AC). DF 2 -PGI 2 was also more potent than PGE 1 , and less potent than PGI 2 as a stimulator of AC activity in platelet homogenates. DF 2 -PGI 2 - and PGI 2 -stimulated AC activity was inhibited by a series of AC inhibitors, SQ 22,536, SQ 4,647 (9-furfuryl adenine) and 2′,5′-dideoxyadenosine. Furthermore, SQ 22,536 inhibited DF 2 -PGI 2 - and PGI 2 -stimulated AC activity in a concentration-related manner, with 150 values of 150 and 300 μM, respectively. Finally, PGE 1 , DF 2 -PGI 2 and PGI 2 , at 0.35 μM induced 2-, 10- and 17-fold increases, respectively, in cyclic AMP levels of intact platelets in platelet rich plasma (PRP). The increase in cyclic AMP levels by PGI 2 and DF 2 -PGI 2 in PRP was also blocked by SQ 22,536. We conclude that DF 2 -PGI 2 , like PGI 2 and PGE 1 , inhibits platelet aggregation by elevating platelet cyclic AMP levels.

Some Biochemical Characteristics of Rodent and Human Mammary Carcinomas

SummaryIn order to establish valid experimental systems for the study of breast cancer, an examination of the biochemical and morphologic characteristics of transplantable and carcinogen-induced mamma

Differences in kidney renin content between normotensive and spontaneously hypertensive rats: effect of captopril treatment

Kidney renin concentrations were significantly lower in spontaneously hypertensive rats (SHR) than in normotensive Wistar Kyoto (WKY) rats. After treatment of both SHR and WKY rats with captopril (100 mg/kg p.o. for 3 months), kidney renin concentration increased dramatically in SHR and slightly, but significantly, in WKY. After captopril treatment, kidney renin content of SHR was still significantly lower than WKY. Because of the lower content of kidney renin in SHR and the proportionately greater increase in kidney renin content in SHR after captopril treatment than in WKY, it is proposed that a fundamental difference(s) in the control of the renin-angiotensin system exists in SHR, an effect which may or may not be related to SHR hypertension.

Inhibition of prostaglandin biosynthesis by SQ 28,852, A 7-oxabicyclo-[2.2.1]heptane analog

7-Oxabicyclo[2.2.1]heptane analogs of prostaglandin (PG) H2 can act as thromboxane (Tx) A2 receptor antagonists or agonists, PGI2 and/or PGD2 receptor agonists, or exhibit a mixture of the above activities. SQ 28,852, a new analog with a hexyloxymethyl omega side chain, is a potent inhibitor of PG synthesis. SQ 28,852 inhibited collagen and arachidonic acid (AA)-induced platelet aggregation and TxB2 and PGE2 formation, but did not block platelet aggregation induced by ADP or the TxA2 mimics, 9,11-azo PGH2, SQ 26,655, and U-46,619. It also blocked conversion of AA to TxB2, PGE2, and 6-keto PGF1 alpha by microsomal preparations of human platelets, bovine seminal vesicles, and bovine aortas, respectively, but did not inhibit the conversion of PGH2 to TxA2 by the platelet microsomal preparation. SQ 28,852 (p.o.) protected mice against the lethal effects of AA (75 mg/kg, i.v.). The I50 values for SQ 28,852, indomethacin and aspirin were 0.025, 0.05 and 15 mg/kg, respectively. Neither SQ 28,852 nor indomethacin protected mice from death caused by 9,11-azo PGH2. SQ 28,852 (0.01 to 1 mg/kg, i.v.) inhibited AA-induced bronchoconstriction in anesthetized guinea pigs for at least 60 min. As an inhibitor of AA-induced bronchoconstriction, SQ 28,852 was 16- and 45-times more potent than indomethacin at 3 and 60 min after i.v. administration, respectively. SQ 28,852 did not inhibit bronchoconstriction induced by histamine or 9,11-azo PGH2, indicating its specificity of action in vivo. SQ 28,852 is the first example of a new class of cyclooxygenase inhibitors whose structure is similar to that of the naturally occurring endoperoxide, PGH2.