Okadaic acid stimulates the ATP-dependent interaction between actin and myosin of smooth muscle via a direct effect on myosin.
The direct effect of okadaic acid (OA) on the ATP-dependent interaction between actin and myosin of smooth muscle was examined not only by the conventional measurement of ATPase activity but also by application of in vitro motility assay developed recently. The motility was effectively enhanced by microM levels of OA. Measurements of the activities of myosin confirmed that the myosin mediated this effect. The result of this study, which was carried out in the absence of protein phosphatase, are not compatible with the recent reports that the stimulatory effect of OA on smooth muscle contraction is attributable to its inhibitory effect on the activity of the protein phosphatase.
Hayakawa
K
K
Department of Pharmacology, Gunma University School of Medicine, Maebashi, Japan.
Okagaki
T
T
Dobashi
T
T
Sakanishi
A
A
Kaneko
K
K
Kohama
K
K
D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002417:Cattle; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005753:Gastric Mucosa / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D009130:Muscle, Smooth / Q000378:metabolism*; D009218:Myosins / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D019319:Okadaic Acid
D000199:Actins; D004988:Ethers, Cyclic; D007476:Ionophores; D019319:Okadaic Acid; D000255:Adenosine Triphosphate; D009218:Myosins; D000252:Calcium-Transporting ATPases