Functional receptor‐channel coupling compared in contractile and proliferative human vascular smooth muscle

Abstract

We have previously identified a human vascular smooth muscle clone that can reversibly convert between proliferative and contractile phenotypes. Here we compared receptor-channel coupling in these cells using fura-2 to monitor [Ca(2+)](i) and patch-clamp to record currents. Histamine elevated [Ca(2+)](i) in all cells and caused contraction of cells exhibiting the contractile phenotype. The rise of [Ca(2+)](i) persisted in Ca(2+)-free solution and was abolished by thapsigargin, indicating involvement of stores. Whole cell electrophysiological recording revealed that histamine evoked transient outward K(+) current, indicating functional receptor-channel coupling. The time-course and amplitude of the histamine-activated current were similar in cells of the proliferative and contractile phenotypes. Moreover, a large conductance K(+) channel was recorded in cell-attached patches and was activated by histamine as well as the Ca(2+) ionophore A-23187, identifying it as the large conductance Ca(2+)-dependent K(+) channel. This K(+) channel showed similar characteristics and activation in both proliferative and contractile phenotypes, indicating that expression was independent of phenotype. In contrast, histamine also elicited an inward Cl(-) current in some contractile cells, suggesting differential regulation of this current depending on phenotype. These studies demonstrate the usefulness of this human vascular cell clone for studying functional plasticity of smooth muscle, while avoiding complications arising from extended times in culture.

Innate Diversity of Adult Human Arterial Smooth Muscle Cells

“…We previously determined that the HITB5 SMC clonal line could briskly contract in response to histamine or angiotensin II. 20,28 The present study established that this was a unifying feature of all spindle-shaped SMC clones. Associated with this were robust calcium transients in response to histamine, angiotensin II, and norepinephrine.…”

“…28 Briefly, cells on a glass coverslip were loosened from the substrate using 1/3 concentration of standard trypsin-EDTA solution (final concentration, 0.075% trypsin-0.03 mmol/L EDTA). This did not itself elicit contraction.…”

Plasticity of KIR channels in human smooth muscle cells from internal thoracic artery

“…These cells bidirectionally switch phenotype, allowing for the comparison of phenotypes while avoiding complications arising from extended time in culture (12,24). This enabled us to demonstrate that loss of the contractile phenotype need not be accompanied by a concurrent loss of large conductance Ca 2ϩ -activated K ϩ channels in SMCs (15), as suggested earlier (22). However, Ca 2ϩ -activated Cl Ϫ current activity was observed exclusively in contractile cells, indicating plasticity of Cl Ϫ channel expression in vascular SMCs (15).…”

“…The chamber was mounted on the stage of a Nikon inverted microscope. For whole cell recordings, the nystatin perforated-patch technique was used, with the electrode solution containing 250 g/ml nystatin, as previously described (15).…”