Adrenergic influence of uterine muscle contractions stimulated by a glycoside from the root of Dalbergia saxatilis.
The mechanism of uterine muscle contraction stimulated by a triterpenoid glycoside (dalsaxin) isolated from the root of D. saxatilis was investigated by in vitro methods in the rat. Dalsaxin caused a dose-related increase in uterine muscle contraction. The contraction was single and transient and was abolished by moderate doses of isoprenaline (1.80 nmol-0.40 mumol) and salbutamol (0.13-25 mumol). Adrenaline (9.10 nmol) also caused a reversible decrease (92.6%; P < 0.01) in myometrial contraction stimulated by this glycoside (0.24 mg/ml). Uterine muscle responses to dalsaxin (0.24 mg/ml) were enhanced by the beta-adrenergic receptor antagonist, propranolol, in a dose related manner. Atipamezole (1.50 ng/ml) but not prazosin (7.72 nmol-15.60 nmol) substantially reduced (80%; P < 0.01) myometrial contractions induced by this uterine spasmogen. The results suggest that dalsaxin enhances uterine muscle contraction by stimulating post junctional alpha 2-adrenergic receptors, presumably by inhibiting plasma membrane adenylate cyclase system and its associated increase in intracellular cAMP content.
Uchendu
C N
CN
Department of Veterinary Physiology & Pharmacology, University of Nigeria, Nsukka, Nigeria.
Leek
B F
BF
D000316:Adrenergic alpha-Agonists / Q000302:isolation & purification / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D007887:Fabaceae / Q000737:chemistry; D005260:Female; D066298:In Vitro Techniques; D018517:Plant Roots / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D014590:Uterine Contraction / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists