Role of adrenergic receptors in mediating estradiol-17 beta-stimulated increases in uterine blood flow of cows.

This study was conducted to investigate the association between estradiol-17 beta (E2 beta) and periarterial alpha and beta-adrenergic receptors in altering blood flow to the bovine uterus. Three nonpregnant Hereford cows were ovariectomized, and an electromagnetic blood flow transducer was placed around the middle uterine artery supplying one uterine horn. A catheter was then placed into a branch of the same artery for infusion of drugs or vehicle. Beginning 3 wk after surgery, uterine blood flow (UBF) of each cow was recorded for 5 min at 20-min intervals throughout a 160-min period three times weekly for 6 wk. Vehicle (.9% NaCl), phentolamine (PHEN, 1 or 10 micrograms) or propranolol (PROP, 1 or 10 micrograms) was infused for 5 min beginning 20 min after the initial UBF measurements, while vehicle or E2 beta (1 microgram) was infused for 5 min beginning at 40 min. Within a week, the first and third 160-min periods contained the same treatment (vehicle or E2 beta), and the second period consisted of vehicle or E2 beta plus PHEN or PROP, allowing for direct comparison of periods 1 and 3 with period 2. Twenty minutes after infusion of E2 beta, UBF was elevated (26.8 +/- 5.4 ml/min; P less than .05) over baseline, reaching a maximal increase at 40 min before starting to decline by 120 min. Uterine blood flow increased (39.2 +/- 7.6 ml/min; P less than .01) during the 5-min infusion of PHEN, and thereafter the magnitude and pattern were similar to those resulting from E2 beta treatment.(ABSTRACT TRUNCATED AT 250 WORDS)