AN HYPOTHESIS FOR THE INTERPRETATION OF THE CONTRACTILE RESPONSE OF VASCULAR SMOOTH-MUSCLE AT THE CELLULAR-LEVEL

The long preservation and recovery of functional (contractile) propert ies in cultured aortic smooth muscle cells, even after replating or de ep-frozen storage and the measurement of their responses are now techn ically settled issues. We could thus study extensively the responses o f single cultured cells from rat thoracic aorta. Responses were elicit ed by the addition of KCI 40 mmol/L without or with a calcium blocker PN 200-100 (10(-6) mol/L); angiotensin II (10(-11)-10(-6) mol/L) witho ut or with antagonist (losartan 10(-5) mol/L); or serotonin (10(-9)-10 (4) mol/L) without or with antagonist (naftidrofuryl 10(-5) mol/L). Re sults thus obtained enabled us to propose a new hypothesis for the int erpretation of the contractile responses of an elastic vascular smooth muscle. The different maximal effects of different agonists result ma inly from the different proportions of cells they can mobilize; the ag onist concentration-contraction relationship is mainly due to the incr ease of the proportion of cells involved up to a maximal value typical of the agonist used. An antagonist primarily reduce the proportion of cells an agonist can mobilize. Some of the consequences of this hypot hesis are briefly outlined.