Quantitation of rat hepatic stellate cell contraction: stellate cells' contribution to sinusoidal resistance

Although it has been hypothesized that contraction of hepatic stellate cell s (HSC) regulates blood flow by modulating sinusoidal resistance, neither H SC contraction nor relaxation has been directly quantitated. To test this h ypothesis, a force transducer was employed to directly measure the magnitud e and rate of contraction and relaxation by primary rat HSC (4.7 x 10(5) +/ - 0.2 x 105 cells) cultured within a collagen gel. Serial exposures to 10% fetal bovine serum stimulated 81 +/- 14 and 82 +/- 10 dyn of contractile fo rce, respectively. Subsequent stimulation with 2 nM endothelin-l (ET-1) res ulted in the development of 185 +/- 25 dyn of force. Contractions began wit hin 10 s of ET-1 stimulation, and the half time of maximal force developmen t was <5 min. Removal of agonist resulted in complete or nearly complete re laxation within 45 min. These results suggest that the magnitude and rate o f HSC contraction and relaxation are capable of modulating blood flow via s inusoidal constriction.