Alan M. Preston

Aldosterone-induced proteins in renal epithelia

Similar aldosterone-induced proteins have been demonstrated in two renal epithelia, the urinary bladder of the toad, Bufo marinus, and epithelia formed by cells of the A6 line derived from the kidney of the toad, Xenopus laevis. The proteins are induced along with the stimulation of Na+ transport but their synthesis is not dependent on Na+ transport per se. In view of the similar characteristics of the aldosterone-induced proteins in these two different epithelia, we suggest that they may have an important role in aldosterone-induced Na+ transport.

Determinants of environmental tobacco smoke in a population of Puerto Rican children

This study was designed to determine among various personal, socioeconomic, and environmental factors those which had the greatest influence on exposure to environmental tobacco smoke (ETS) in a population of children residing in a tropical environment and to compare these results with those obtained in the literature of tobacco exposed children in temperate climates. Urine specimens were collected from 606 healthy Puerto Rican children (2-12 years) living in an industrial area and analyzed for cotinine, a quantitative biomarker for exposure to ETS. Parents completed a questionnaire covering smoking habits and socioeconomic information. Seventy per cent of the children were reported to be exposed to ETS, 50% resulting from exposure to smoke from either or both parents. Major determinants to ETS exposure were found to be presence of smoker, number of smokers, identity of smoker, number of cigarettes smoked in the household and child age with the youngest children suffering twice the exposure of older children. Non-determinants were exposure to smoke other than from the parent, sex of the child, season of the year and several socioeconomic factors including civil and employment status of the mother, mothers age and educational background and whether food stamps were being received. Results of a multiple regression analysis showed that our predictors accounted for 40% of cotinine appearing in the urine. Reasons for this relatively low value may be due in part to precision of our analytic method and lower levels of ambient smoke in our population vs. others that reported higher R(2) values. Predictions from questionnaire information for high ETS exposure were not always the same as those indicated by urinary cotinine emphasizing that the bioindicator, which indicates the actual inhalation of ETS, is a better predictor of exposure than responses from a questionnaire.

Effect of (-) delta 9 THC on ATPase systems from various sources.

Chromatographically pure Δ9-tetrahydrocannabinol (Δ9THC) and other cannabinoids were tested for inhibitory activity on sodium and potassium stimulated ATPase (ATP phosphohydrolase, EC 3.6.1.3) from various sources. We found out that in addition to inhibiting Na+ and K+ dependent ATPases, Mg+ + ATPases were inhibited as well. Rat brain ATPases were much more sensitive to Δ9THC than to equal concentrations of ouabain. Inhibition by Δ9THC was shown to occur both in situ and in vitro. In vitro, an I50 of 3 × 10-6 M was calculated for enzyme preparations of specific activity of 1,200–1,800 nmoles Pi/min/mg protein. The drug was found to bind to the enzyme and to cause a marked increase in Km for Na+, but no change in the Km for K+. These results suggest that Δ9THC inhibits (Na + K) ATPases by interfering with the phosphorylation in the sequence of reactions leading to ATP hydrolysis. Phosphatidyl ethanolamine was found to reverse the inhibition caused by Δ9THC in these enzyme preparations. In Ehrlich ascites tumor cells (107 cells/flask) 60 μM Δ9THC inhibited nucleoside ([3H] thymidine) incorporation without exerting any significant effect on the viability of cells as measured by O2 consumption. Particulate ATPases isolated from cells exposed to Δ9THC had significantly lower activity than cells in control media, 123 ± 36 vs. 172 ± 16 nmoles Pi/min/mg protein (p < 0.005, n = 16). Thus a correlation seems to exist between ATPase inhibition and nucleoside uptake. A thorough study of the effect of cannabinoids on membrane bound ATPases deserves to be undertaken.

BLOOD GLUCOSE AND NON-ENZYMATIC GLYCATION OF PROTEINS IN RATS INJECTED WITH LOW-DOSE STREPTOZOTOCIN AND FED DIETS EITHER HIGH IN SUCROSE OR STARCH

Abstract The purpose of this investigation was to study the effect of dietary carbohydrate (CHO) at a set level but in two different forms on non-enzymatic glycation (NEG) of blood proteins in rats, injected with a low dose of diabetogen. Rational for this approach is that glycemic response would be under a greater influence of dietary CHO at threshold doses of the diabetogenic agent. Therefore, streptozotocin (Sz) was injected (30 mg/kg) into rats fed an AIN76 diet (68.5% of cal as CHO) having a sucrose:starch ratio of 50:15 (SUCROSE DIET) or an equicaloric modified diet with a ratio of 15:50 (STARCH DIET). Control rats were fed similar diets but injected with buffer. Rats were fed these diets for 1 wk, injected with Sz and fed 6 more wks. Weights were recorded weekly and blood collected bi-weekly and analyzed for glucose and for glycated hemoglobin (Gly Hb) an indicator of NEG. Responses of weight, glucose levels and Gly Hb within groups of rats varied widely with some Sz-injected rats having severe diabetic symptoms while others had values resembling controls. No statistically significant differences were noted in weight, glucose or Gly Hb between dietary groups. It is concluded that form of CHO has no effect on blood glocose and NEG of proteins in rats in an early diabetic stage.