Prostaglandin I2 does not contribute to the hypotensive effect of the superoxide dismutase mimetic Tempo in rats with aortic coarctation-induced hypertension.

This study was designed to investigate the contribution of prostaglandins to the vasodepressor effect of the superoxide dismutase mimetic Tempo in rats made hypertensive by ligation of the abdominal aorta at a point between the left and right renal arteries. Rings of thoracic aorta taken from rats with aortic coarctation released more 6-keto-PGF1alpha (a non-enzymatic product of PGI2 degradation) in the presence than in the absence of Tempo (1 mmol/L; 35.3 +/- 10.1 versus 13.6 +/- 2.6 pg/mg tissue). However, Tempo administered intravenously (2 mg/kg bolus injection plus infusion at 3 mg/kg/h) to rats with aortic coarctation did not increase significantly the concentration of 6-keto-PGF1alpha in vena cava blood. Treatment with Tempo did not affect the arterial pressure of un-operated normotensive rats but promptly decreased the arterial pressure of rats with aortic coarctation-induced hypertension (from 178 +/- 2 to 125 +/- 6 mmHg). The vasodepressor effect of Tempo in hypertensive animals was not affected by pretreatment with indomethacin to inhibit prostaglandin synthesis. These data argue against the hypothesis that PGI2 contributes to the acute hypotensive effect of Tempo in rats with aortic coarctation.

Lipoxygenase-dependent mechanisms in hypertension.

This study was designed to examine the contribution of lipoxygenase products to mechanisms of vascular contraction and elevated blood pressure in rats with aortic coarctation-induced hypertension. In cytosolic fractions of aortae taken from hypertensive rats, 12-lipoxygenase protein was increased as compared to normotensive controls. Aortic rings from hypertensive, but not from normotensive rats, exhibited a basal tone which was reduced 74+/-12 and 71+/-22%, respectively, by the lipoxygenase inhibitors cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC, 10(-5) mol/L) and 5,8,11-eicosatriynoic acid (ETI, 10(-5) mol/L). CDC (8 mg/kg s.c.) did not affect the blood pressure of normotensive rats but decreased that of hypertensive rats from 182+/-6 to 151+/-10 mm Hg. The blood pressure lowering effect of CDC was blunted in hypertensive rats pretreated with indomethacin or antibodies against 5,6-dihydro-prostaglandin I2. These data suggest contribution of lipoxygenase-derived products to mechanisms underlying aortic smooth muscle basal tone and elevated blood pressure in rats with aortic coarctation-induced hypertension. The vasodepressor effect of CDC depends on a mechanism involving vasodilatory prostaglandins.

A return to the past: a student perspective on medical school pharmacology.

In 1989, the second-year medical school pharmacology course at New York Medical College was revised to help improve student and faculty morale, improve scores on class exams and the U.S. Medical Licensing Examination (USMLE), and encourage more active student participation in the course. Rather than incorporating new and innovative teaching techniques, the course adapted a more classical presentation of material. Traditional blackboard lectures replaced lectures aided by the use of slides, overheads, and extensive handouts. Transcripts and the tape recording of lectures were prohibited. Higher standards for students were set with the implementation of a passing grade, initially set at 65% and increased to 66%. Review sessions with senior graduate students were incorporated, and the use of live animal demonstrations was continued. Despite the return toward a more traditional classroom, students' satisfaction with the course continues to be high, with an overall 80% satisfaction rating. Attendance at lectures is quite high (> or = 80%). In addition, student scores on the USMLE continue to improve, and the number of students failing pharmacology continues to decrease. Overall, these trends indicate that the changes implemented in the pharmacology course at New York Medical College in 1989 successfully improved student participation in class and performance in the course and on the USMLE.

Involvement of nitric oxide and potassium channels in the reduction of basal tone produced by blockade of thromboxane A2/prostaglandin H2 receptors in aortic rings of hypertensive rats.

This study was designed to investigate involvement of potassium channels in the action of nitric oxide facilitating reduction of basal tone by thromboxane A2/prostaglandin H2 receptor blockade with ifetroban in rings of thoracic aorta taken from rats with aortic coarctation-induced hypertension. Ifetroban-induced reduction of basal tone in aortic rings without drug pretreatment was attenuated (P<0.05) in rings pretreated with the nitric oxide synthesis inhibitor N(omega-nitro-L-arginine methyl ester (L-NAME; 3 x 10(-4) mol/L; 0.55+/-0.09 g versus 0.23+/-0.07 g). The vasorelaxing effect of ifetroban also was decreased (P<0.05) in preparations pretreated with a potassium channel blocker, either tetraethylammonium (TEA; 10(-2) mol/L) or 4-aminopyridine (4-AP; 3 x 10(-3) mol/L). Ifetroban-induced reduction of basal tone was not attenuated in preparations pretreated first with L-NAME and then with sodium nitroprusside (SNP; 6+/-1 nmol/L) to compensate for the loss of endogenous nitric oxide. However, the facilitatory effect of SNP on ifetroban-induced relaxation of aortic rings pretreated with L-NAME alone was not demonstrable in rings pretreated with L-NAME plus TEA or 4-AP. These observations suggest that a mechanism involving nitric oxide and potassium channels facilitates the reduction in basal tone produced by ifetroban in aortic rings of rats with aortic coarctation-induced hypertension.

Prostaglandin I2 contributes to the vasodepressor effect of baicalein in hypertensive rats.

Lipoxygenase inhibitors reduce blood pressure in hypertensive rats. The vasodepressor effect of lipoxygenase inhibitors may be related to increased production of prostaglandin (PG) I2 since lipoxygenase-derived fatty acid hydroperoxides inhibit PGI2 synthase. This hypothesis was examined in rats made hypertensive by infusion of angiotensin II (200 ng/min i.p.) for 12 to 14 days. In hypertensive but not in normotensive rats, the lipoxygenase inhibitor baicalein (60 mg/kg s.c.) increased (P<.05) the conversion of exogenous PGH2 to PGI2 by aortic segments, the release of 6-keto-PGF1alpha by aortic rings, the concentration of 6-keto-PGF1alpha in blood, and the renal excretion of 6-keto-PGF1alpha. Treatment with baicalein did not affect the blood pressure of normotensive rats but decreased the blood pressure of hypertensive rats from 177+/-8 to 133+/-9 mm Hg after 120 minutes (P<.05). Also, the lipoxygenase inhibitor cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (8 mg/kg s.c.) was without effect on the blood pressure of normotensive rats but decreased the blood pressure of hypertensive rats from 182+/-4 to 139+/-8 mm Hg (P<.05). However, the blood pressure of hypertensive rats pretreated with indomethacin (5 mg/kg i.v.) was affected by neither baicalein nor cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate. Moreover, in hypertensive rats in which baicalein had decreased blood pressure to 148+/-6 mm Hg, the administration of rabbit serum containing antibodies against 5,6-dihydro-PGI2 (0.3 mL i.v.) partially reversed the response to baicalein, increasing blood pressure to 179+/-7 mm Hg within 20 minutes (P<.05). The antibodies also were shown to block the vasodepressor effect of PGI2 but not of PGE2. Collectively, these data suggest contribution of PGI2 to the acute antihypertensive effect of baicalein in rats with angiotensin II-induced hypertension.

Contribution of constrictor prostanoids to the calcium-dependent basal tone in the aorta from rats with aortic coarctation-induced hypertension: relationship to nitric oxide.

Rings of thoracic aortae taken from rats made hypertensive by aortic coarctation express a calcium-dependent basal tone. We investigated whether this basal tone is mediated by prostanoids. To this end, we contrasted the effects of indomethacin, an inhibitor of cyclooxygenase, and of ifetroban, an antagonist of thromboxane A2/prostaglandin endoperoxide H2 receptors, on basal tone in aortic rings taken from normotensive and hypertensive rats. Rings with endothelium from normotensive rats were unaffected by indomethacin and ifetroban. However, in endothelium-intact rings from hypertensive rats, the basal tone was reduced 65 to 75% by indomethacin and ifetroban, but not by CGS13080, an inhibitor of thromboxane synthase. The reductions in tone elicited by indomethacin and ifetroban in rings from hypertensive rats were eliminated upon removal of the endothelium and were attenuated when the rings were pretreated with an inhibitor of nitric oxide synthase (N omega-nitro-L-arginine methyl ester or N omega-nitro-L-arginine) or an inhibitor of soluble guanylate cyclase. Neither indomethacin nor ifetroban affected tissue cGMP levels or nitrite release in aortic rings taken from hypertensive rats. However, sodium nitroprusside offset the inhibitory effects of N omega-nitro-L-arginine methyl ester, on the relaxant responses to indomethacin and ifetroban. These data suggest that a constrictor prostanoid other than thromboxane A2, presumably prostaglandin endoperoxide H2 contributes to the implementation of the basal tone in rings from hypertensive rats and that part of the relaxant response to indomethacin and ifetroban is linked to nitric oxide.

TNF-mediated cytotoxicity and resistance in human prostate cancer cell lines.

BACKGROUND: The contribution of TNF receptor (TNF-R) expression was investigated with respect to TNF sensitivity or insensitivity for androgen-dependent and androgen-independent human prostate cancer (PCA) cell lines, respectively. METHODS: Flow cytometric analyses using monoclonal antibodies against the 55-kDa receptor (TNF-R1) and the 75-kDa receptor (TNF-R2) indicated that both receptors were expressed on all three cell lines. RESULTS: Moreover, expression of TNF-R1 was greater than expression of TNF-R2 in these PCA cells. All three PCA cell lines produced IL-6. However, IL-6 production was enhanced when TNF-insensitive JCA-1 and PC-3 cells, but not TNF-sensitive LNCaP cells, were treated with rTNF (10(-9) M). CONCLUSIONS: These data suggest that the lack of an antiproliferative effect of rTNF on the androgen-independent PCA cell lines PC-3 and JCA-1 is not due to the failure of these cells to express TNF-R, but may be related to the differences in TNF-mediated IL-6 expression by these PCA cell lines.

Cytochrome P450 inhibitors attenuate the hypotonic shock-induced increases in K+ efflux in LLC-PK1 cells.

Cell volume regulation in LLC-PK1 cells was evaluated by measuring 86Rb efflux (rate constant), used as an indicator of K+ efflux. Hypotonic shock induced a transient increase in the rate constant which returned to baseline values after 15 min. ETYA, an arachidonic acid-competitive antagonist as well as the cytochrome P450 inhibitors SKF 525-A, clotrimazole and 7-ethoxyresorufin, inhibited the hypotonic shock-induced increment in the rate constant. Arachidonic acid did not change hypotonic shock-induced increments in K+ efflux. LLC-PK1 cells were unable to metabolize 14C-arachidonic acid. We concluded that although arachidonic acid inhibitors block the hypotonic shock-induced increment in K+ efflux, this effect cannot be related to inhibition of arachidonic acid metabolism.

Effect of tumor necrosis factor-alpha and interferon-gamma on the growth of human prostate cancer cell lines.

Human recombinant tumor necrosis factor-alpha (rTNF-alpha, 10(-12)-10(-8) M) inhibited the proliferation of androgen-dependent LNCaP cells by 32-56%. In contrast, proliferation of androgen-independent PC-3 and JCA-1 cells was only slightly inhibited, or not inhibited at all, respectively. Human recombinant interferon-gamma (rIFN-gamma, 500 U/ml) decreased proliferation of PC-3 and JCA-1 cells by 35% and 53%, respectively, but had no effect on LNCaP cells. Interestingly, the combination of rIFN-gamma and TNF-alpha had greater antiproliferative effects on JCA-1 cells than treatment with either cytokine alone. However, the antiproliferative effects of this combination were similar to those observed for PC-3 or LNCaP cells treated with rIFN-gamma or TNF-alpha alone, respectively. These data suggest that some forms of androgen-independent prostate cancer may benefit from a combination therapy of IFN-gamma and TNF-alpha, while the use of IFN-gamma alone may be more efficacious in others.

Natriuretic action of angiotensin(1-7).

Evidence that angiotensin(1-7) (Ang(1-7)) is biologically active and can be synthesized by the kidney prompted us to examine its actions in the rat, isolated kidney. Ang(1-7) had three major effects producing, (1) a substantial natriuresis and diuresis, (2) an increase in urinary sodium concentration associated with a fall in potassium concentration and (3) an increase in glomerular filtration rate without affecting renal vascular resistance. Thus, Ang(1-7) may participate in the renal effects of the renin-angiotensin system.