Bovine Carotid Artery Smooth Muscle Research Articles

Effects of Nitrendipine on Growth Activity in Cultured Vascular Smooth Muscle Cells

Proliferation and migration of smooth muscle cells (SMCs) in the arterial wall may play a role in the development of atherosclerosis and hypertension. If cell migration and proliferation are dependent on extracellular calcium, then treatment with calcium channel blockers such as nitrendipine may alter these cellular responses. In the studies reported here, proliferation and migration activities were assessed in cultured bovine carotid artery smooth muscle cells exposed to nitrendipine. SMCs in long-term culture are characterized by periods of either stable or enhanced proliferative activity. During the stable periods, 1 microM nitrendipine has no effect on proliferation, but during periods of enhanced proliferation, 1 microM nitrendipine augments growth by approximately 20%. SMC migration rates and interdivision times were determined from analysis of time-lapse cinematography films. During stable periods of growth, cell migration rate was inversely related to interdivision time (i.e., fast migrating cells had the shortest interdivision times). Treatment with 1 microM nitrendipine abolished the relationship between migration rate and interdivision time and prolonged interdivision times. These data suggest that the ability of nitrendipine to alter SMC proliferation, interdivision time, and migration is dependent upon the overall proliferative state of the culture.

Pharmacology and force development of single freshly isolated bovine carotid artery smooth muscle cells.

Most studies of mammalian vascular smooth muscle cell mechanics and pharmacology have relied upon data from intact tissue preparations. The purpose of this study was to determine how single mammalian vascular smooth muscle cell pharmacological sensitivity to histamine and force development compared to the intact tissue from which it was derived. Thus, techniques were developed for isolating large numbers (5 X 10(5) cells/ml) of cells from bovine carotid arteries. Single cells were spindle-shaped with dimensions of 117 +/- 11 (SE) micron in length by 7 +/- 1 (SE) micron in diameter (n = 27). The effect of histamine concentration on cell length was studied in suspensions of freshly isolated cells. Histamine concentration-response curves revealed that single smooth muscle cells shortened to histamine concentrations in a graded fashion, and that shortening was mediated through histamine H1 receptors. The threshold for 10% of maximum response occurred at 8.0 X 10(-11) M histamine. This threshold was at least three orders of magnitude lower than the threshold for 10% of maximum tension in the intact tissue under isometric conditions. In addition to cellular pharmacology, mechanical studies were performed by tying a single cell to an ultrasensitive force transducer. Active stresses of 0.5 +/- 0.1 X 10(5) N/m2 (n = 4) were measured in response to electrical stimulation for cells in low extracellular calcium (0.5 mM). These data suggest that histamine sensitivity and smooth muscle cell mechanics may best be determined in single cell studies that minimize diffusional barriers to agonist and avoid intercellular interactions that are present in the intact tissue.

Calcium messenger system: an integrated view.

Calcium messenger system: an integrated view.

Multiple forms of cyclic nucleotide phosphodiesterase from bovine carotid artery smooth muscle

DEAE-cellulose chromatography, in the presence and absence of Ca 2+, of the 16,000 g supernatant from bovine carotid artery smooth muscle has been used to separate four different types of cyclic nucleotide phosphodiesterase (3′:5′-cyclic-nucleotide 5′-nucleotidohydrolase, EC 3.1.4.17) activity, designated types A, B, C, and D. Type A is a high affinity, cyclic AMP-specific form of phosphodiesterase ( K m = 1.6 μM) and elutes at relatively high ionic strength. Type B is a high affinity ( K m = 2 μM), cyclic GMP-specific form which elutes at low ionic strength. Type C is a mixed substrate form, displaying anomalous kinetics for the hydrolysis of both cyclic AMP and cyclic GMP. It elutes from DEAE-cellulose at an ionic strength intermediate to that of types A and B. Type D is also a mixed substrate form of phosphodiesterase. However, its elution pattern from DEAE-cellulose differs, depending on whether Ca 2+ is present or not, suggesting a Ca 2+-dependent interaction between this enzyme form and the acidic Ca 2+-dependent regulator protein (CDR). The hydrolytic activity of type D is stimulated by CDR, and activation requires the simultaneous presence of Ca 2+ and CDR. Kinetic analysis of cyclic AMP hydrolysis by type D gives a linear double reciprocal plot; activation has no effect on the K m but increases the velocity approximately sixfold. Activation of cyclic GMP hydrolysis apparently affects both the K m and V. At all concentrations tested, the degree of activation is higher with cyclic AMP than with cyclic GMP. It is suggested that while the activable form of phosphodiesterase may play a relatively minor role in the overall hydrolysis of cyclic nucleotides, Ca 2+-dependent activation may have a more important role in regulating the level of cyclic AMP than that of cyclic GMP in vascular smooth muscle.