INTRACELLULAR-RECORDING AND DYE TRANSFER IN ARTERIOLES DURING BLOOD-FLOW CONTROL

We tested for dye coupling between arteriolar smooth muscle cells (SMC) and endothelial cells (EC) and investigated the correspondence of vasomotor activity with changes in the membrane potential (V(m)) of EC and SMC during blood flow control. Female golden hamsters (n = 8, 90-170 g) were anesthetized (pentobarbital sodium, 60 mg/kg ip). A check pouch was spread over an optical pedestal, transilluminated, and irrigated with physiological saline solution (37-degrees-C, pH 7.4). Glass microelectrodes were filled with 3 M KCl or with Lucifer yellow dye (LY, mol wt 470; 106 mM). SMC or EC of arterioles (ID, 20-50-mu-m) containing blood flow were impaled under a stereomicroscope. V(m) was similar [-48 +/- 3 and -52 +/- 4 mV (means +/- SE)] with KCl (n = 6) or LY (n = 13) microelectrodes, respectively. Acetylcholine (5 x 10(-6) M) increased V(m) from -47 +/- 3 to -67 +/- 4 mV (n = 5; P < 0.01) concomitant with vasodilation. Spontaneous slow waves in V(m) (2/min, 15-30 mV) were observed in arterioles with vasomotion. In cells identified with LY microinjection, resting V(m) was -52 +/- 8 and -44 +/- 2 mV for EC (n = 3) and SMC (n = 3), respectively. SMC injected with LY did not show evidence of dye transfer to other SMC or to EC. When an EC was injected, the dye spread to many contiguous EC but not to SMC. Findings indicate that EC-to-EC coupling provides a pathway for cell-to-cell conduction along the arteriolar wall and that changes in V(m) of EC and SMC correspond with vasomotor activity in arterioles during blood flow control.