TRPC channels are a group of Ca(2+)-permeable nonselective cation channels that mediate store-operated and/or agonist-stimulated Ca(2+) influx in a variety of cell types. In this study, we extensively examined the expression patterns of TRPC homologs in human vascular tissues. RT-PCR amplified cDNA fragments of TRPC1 (505 bp), TRPC3 (372 bp), TRPC4 (499 bp), TRPC5 (325 bp), TRPC6 (509 bp), and TRPC7 (187 bp) from RNA isolated from cultured human coronary artery endothelial cells. In situ hybridization yielded strong labeling of TRPC1,3-6 in the endothelial and smooth muscle cells of human coronary and cerebral arteries. TRPC7 labeling was exclusively found in endothelial cells but not in smooth muscle cells. Results from immunohistochemical staining were consistent with those from in situ hybridization. Similar expression patterns of TRPC homologs were also observed in arterioles and vaso vasora. In conclusion, our study indicates that TRPC homologs are widely expressed in human vessels of all calibers, including medium-sized coronary arteries and cerebral arteries, smaller-sized resistance arteries, and vaso vasora. These results suggest a ubiquitous role of TRPC homologs in regulating blood supply to different regions and in controlling arterial blood pressure.

Abstract-Hemodynamic shear stress elicits a rise in endothelial [Ca 2ϩ ] i , which may serve as a key second messenger to regulate many flow-associated physiological and biochemical processes. In the present study, we used Mn 2ϩ quenching of fluorescent dye Fluo3 as an assay to investigate the Ca 2ϩ influx of rat aortic endothelial cells in response to flow. We found that the Ca 2ϩ signaling in response to flow could be greatly influenced by the status of intracellular Ca 2ϩ stores. Depletion of intracellular Ca 2ϩ stores by thapsigargin (4 mol/L) or cyclopiazonic acid (10 mol/L) drastically sensitized the Ca 2ϩ influx in response to flow. Ca 2ϩ -mobilizing agonist bradykinin (100 nmol/L) or ATP (100 mol/L) had similar sensitizing effect. The effect of bradykinin or ATP was blocked by Xestospongin C and U73122, suggesting that the sensitization was related to the IP 3 -mediated store depletion. On the other hand, the Mn 2ϩ quenching in response to flow was greatly reduced by ochratoxin A (100 nmol/L), an agent that could increase the filling state of intracellular Ca 2ϩ stores. In addition, we found that depletion-sensitized Ca 2ϩ influx in response to flow was mediated by a PKG-inhibitable cation channel and that the influx was affected by membrane potential and K ϩ channel activity. In conclusion, the present study argues for a critical role of intracellular Ca 2ϩ status in determining the Ca 2ϩ signaling in response to flow and it provides a general mechanistic explanation for the stimulatory role of blood-borne agonists on flow-induced Ca

Recent epidemiological studies have suggested that weight cycling induced by repeated dieting over time may increase the risk of cardiovascular disease. It is speculated that the increased mortality from coronary heart disease for people with a history of excessive weight cycling could be attributed to change in lipid metabolism. Previous studies have demonstrated that repeated cycling of 100% food restriction followed by ad libitum refeeding caused a depletion of linoleate and alpha-linolenate in rats. The objective of the present study was to test the hypothesis that the weight cycling-induced reduction in linoleate and alpha-linolenate is independent of extent of calorie restriction. Two consecutive weight cycles in three experiments were induced by 100% calorie restriction, 60% calorie restriction, and 36% calorie restriction, respectively, followed by ad libitum refeeding. As the consequence of the two weight cycles, linoleate and linolenate were decreased, whereas myristate, palmitate, and palmitoleate were proportionally increased in carcass and adipose tissue lipids. The results of all three experiments showed a preferential depletion of linoleate and alpha-linolenate without changes in final body weight, total body fat, and adipose tissue pads in the weight-cycled rats. In addition, the triacylglycerol species profile in the adipose tissue of weight-cycled rats was significantly remodeled, with a proportional depletion of linoleate-enriched triacylglycerol species (LLL, LLO, and LLP, where L, O, and P are linoleic, oleic, and palmitic acid, respectively) and a proportional accumulation of palmitate-enriched triacylglycerol species (OPPo, PPPo, and PPP, where Po is palmitoleic acid). We conclude that weight cycling changes the ratio of polyunsaturated fatty acids to saturated fatty acids and remodels the adipose tissue triacylglycerol species profile in rats.