Uptake of atrial natriuretic peptide and production of cGMP in cultured human glomerular endothelial cells

Interactions between human glomerular endothelial cells and atrial natriuretic peptide (ANP) were studied with 125I-alpha-human-ANP binding and intracellular accumulation of cGMP. Uptake for alpha-hANP (1-28 or 5-28) by homogeneous cultures of human glomerular endothelial cells was dose and time dependent with optimal uptake occurring after 30 min of incubation at 37 degrees C. Scatchard analysis of the specific binding data with a two-compartmental model identified both high (Kd = 0.3 nM)- and low (Kd = 10 nM)-affinity receptors, with a binding site density of 12,000 and 18,060 receptors per cell, respectively. alpha-hANP markedly stimulated glomerular endothelial cell-associated cGMP. After a 2-min incubation, cGMP increased 1.3-fold (from 17.88 +/- 1.29 to 23.33 +/- 3 pmol/mg of protein), in the presence of 1 nM ANP, to more than threefold (from 21 +/- .1 to 80.5 +/- 14.5 pmol/mg of protein) with 1 microM ANP (P < 0.05). In contrast, a 10 microM concentration of the clearance receptor C-ANP4-23 increased cGMP by 1.6 +/- 0.6 fold. ANP stimulation of intracellular cGMP was 100 times more sensitive in human glomerular endothelial than in mesangial cells. In comparison, higher doses of bradykinin were necessary to evoke similar responses in glomerular endothelial cells. In the presence of 10 microM bradykinin, cellular cGMP increased by 1.75 +/- 0.6-fold versus control cells. However, unlike ANP, bradykinin-stimulated cGMP synthesis was significantly inhibited by prior treatment with oxyhemoglobin (10(-5) M), an inhibitor of soluble guanylate cyclase, and NG-nitro-L-arginine (NO2Arg), a specific inhibitor of endothelial-derived relaxing factor (EDRF).(ABSTRACT TRUNCATED AT 250 WORDS)

Thiopurine methyltransferase activity in a sample population of black subjects in Florida

Thiopurine methyltransferase (TPMT), is an enzyme detected in the human red blood cell that catalyzes the S-methylation of thiopurine drugs and is known to exist as a genetic polymorphism in white subjects. Investigations in this laboratory of red blood cell TPMT showed interethnic differences also existed in North American black subjects. A sample group of black subjects in Florida had a mean activity of 8.64 +/- 3.47 U/ml red blood cells and an antimode of 6.5 units, which represented values significantly lower than those obtained for both the mean activity and the antimode in other populations. The findings of this study suggest the possibility that TPMT activity may be under genetic control in North American black subjects and that this ethnic group may be at greater risk of experiencing thiopurine-induced toxicity caused by the lower overall mean activity of the enzyme.

A pilot clinical and pharmacological study of intra-arterial infusion of thiotepa

Fourteen patients with progressive localized tumors were treated on a clinical and pharmacological study with intra-arterial Thiotepa. A transfemoral percutaneous catheter was inserted into the major artery supplying the tumor. A venous catheter was inserted into the vein draining the tumor area for blood sampling. Doses of Thiotepa ranged from 0.3 mg/kg to 1.0 mg/kg. Courses were repeated monthly and doses of drug escalated as tolerated. Toxicity was mild and doses of drug at least up to 0.9-1.0 mg/kg were tolerable. Pharmacokinetic parameters suggest increasing binding of Thiotepa to tissue when the drug is administered by the intra-arterial route. Clinical responses were observed in a patient with melanoma and in another patient with unknown primary cancer.

Clinical and pharmacological study of intrahepatic artery infusion of thiotepa

Twenty patients with primary or metastatic liver cancer were treated on a clinical and pharmacological study with intrahepatic artery infusion of Thiotepa. Toxicity was tolerable and included nausea and fatigue. Uncommon side effects were myelosuppression, abdominal pain and anemia. One patient with gallbladder cancer had a partial response for 11 (+) months. Recommended dose of Thiotepa for future Phase II clinical trials is 1.0 mg/kg. Pharmacokinetics of intrahepatic Thiotepa revealed an extraction ratio similar to that reported for cisplatin. The data suggest increased hepatic clearance for Thiotepa either by binding or metabolism.

Lidocaine pharmacokinetics during water immersion in normal humans

Water immersion produces a marked diuresis, natriuresis, and kaliuresis in association with suppression of the renin-aldosterone system. These effects are mediated primarily by an increase in central blood volume. Consequently, this redistribution and the resultant marked increase in cardiac output is associated with alterations in the circulating levels of several volume regulatory hormones, including plasma renin activity and plasma aldosterone. Although the changes in these blood hormonal levels probably reflect perturbation of hormonal release, it is conceivable that the above-mentioned central hemodynamic modifications result in an altered splanchnic blood flow, thereby modulating hormonal clearances. We assessed the effects of immersion on hepatic blood flow by determining the pharmacokinetics of single doses of lidocaine administered intravenously. Seven normal male subjects were studied during a time-control period and during water immersion to the neck. The clearance of lidocaine was unaltered by immersion, suggesting that the presumed marked central hypervolemia and increased cardiac output was not associated with changes in splanchnic blood flow.

Purification and Properties of Human Lymphocyte Activating Factor (LAF)

Lymphocyte-activating factor (LAF) has been shown to be produced by LPS-stimulated human adherent cells (monocytes) and peripheral leukocytes, but many non-macrophage cell lines failed to produce LAF. Other macrophage activators including latex microspheres, antigen-antibody complexes, and barium sulfate induce the production of LAF. There is a delay of 6 hr before significant amounts of LAF activity appear in the supernatant medium and maximum activity is found after 12 to 24 hr.

Chromatography of concentrated crude supernatant fractions containing LAF activity on Sephadex G-100 gave two peaks of activity (approximately 85,000 and 13,000 daltons). The latter constitutes the major activity and has been purified at least 500-fold with Sephadex G-100, anion exchange, and adsorption chromatography. Optimal stimulation with LAF induces mitosis in 10% of murine thymocytes. The purified activity is sensitive to chymotrypsin and is not affected by treatment with sodium periodate, sulfhydryl reagents, and phenylmethanesulfonylfluoride.

The response of thymocytes to LAF decreases with age after 10 weeks and thymocytes obtained from animals injected with cortisone or tumor-bearing animals have an increased responsiveness to LAF.

Purification and properties of human lymphocyte activating factor (LAF)

Lymphocyte-activating factor (LAF) has been shown to be produced by LPS-stimulated human adherent cells (monocytes) and peripheral leukocytes, but many non-macrophage cell lines failed to produce LAF. Other macrophage activators including latex microspheres, antigen-antibody complexes, and barium sulfate induce the production of LAF. There is a delay of 6 hr before significant amounts of LAF activity appear in the supernatant medium and maximum activity is found after 12 to 24 hr. Chromatography of concentrated crude supernatant fractions containing LAF activity on Sephadex G-100 gave two peaks of activity (approximately 85,000 and 13,000 daltons). The latter constitutes the major activity and has been purified at least 500-fold with Sephadex G-100, anion exchange, and adsorption chromatography. Optimal stimulation with LAF induces mitosis in 10% of murine thymocytes. The purified activity is sensitive to chymotrypsin and is not affected by treatment with sodium periodate, sulfhydryl reagents, and phenylmethanesulfonylfluoride. The response of thymocytes to LAF decreases with age after 10 weeks and thymocytes obtained from animals injected with cortisone or tumor-bearing animals have an increased responsiveness to LAF.