Quantitative aspects of electrical and mechanical responses to anisosmolar solutions in the smooth muscle of the rat portal vein.
The electrical and mechanical activity of the rat portal vein were studied quantitatively under prolonged exposure to solutions in which osmolality was varied by changes in sucrose content. Reducing osmolality by 15 or 30 mosm/kg below the control value of 290 mosm/kg caused enhanced electrical and mechanical activity whereas hyperosmolality up to 390 mosm/kg led to inhibition as demonstrated earlier. These responses faded under prolonged exposure. In hypoosmolality integrated mechanical activity returned to control after about 10-15 min while spike activity remained somewhat increased. Prolonged hyperosmolality was associated with return of spike discharge towards control frequency whereas the integrated contractile force reverted from initial inhibition to levels above control after some 10-15 min. Therefore, the integrated force per spike was increased by prolonged hyperosmolality and decreased by hypoosmolality. Variation in osmolality had similar effects on the amplitude of K+ contractures. The time course of the osmotic responses are discussed in relation to the dynamic effects of passive stretch and shortening in the portal vein. The relation that may exist between "intropic" effects of osmolality and the contractures obtained in strongly hypertonic media is considered.
D000818:Animals; D004594:Electrophysiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009994:Osmolar Concentration; D011169:Portal Vein / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013395:Sucrose / Q000008:administration & dosage; D013997:Time Factors
D013395:Sucrose