Vol. 7, Issue 8 (2018)

Author(s):
Harithalakshmi Jandhyam, Soumya Ranjan Rout and Subas Chandra Parija

Abstract:
The present study investigates the role of NO in vasorelaxation of middle uterine artery obtained from non-pregnant (NP) and pregnant (P) Capra hircus (Ch). Uterine artery rings (1.5-2 mm) were mounted in a four chambered automatic organ bath containing 20 ml MKHS, maintained at pH 7.4. Following 1hr equilibration, Phenylephrine (PE) was added to bath in cumulative dose (1ηM-10μM) or in single dose (1μM) to induce contraction. ACh (10ηM-10μM) was added cumulatively to the bath either in absence or presence of L-NAME or Indomethacin or combination of L-NAME and Indomethacin or SNP (10ηM-10μM) to relax PE-precontracted rings. Isometric contraction was recorded using highly sensitive force transducer connected to power Lab (8/16) data acquisition system. The maximal contraction (E_max) obtained from CRC of PE elicited in MUA of P Ch ( 2.19± 0.26g) was significantly greater than that of NP Ch (1.61±0.01g). PE-induced sustained contraction (100%) was reduced to 67.77%, 57.88% by ACh and 47.28%, 31.30% by SNP in MUA of NP and P Ch, respectively. Endothelium removal in MUA rings almost abolished ACh –contraction in NP and P Ch. In presence of L-NAME or Indomethacin or L-NAME and Indomethacin, ACh-induced contraction was augmented to 90.54%, 74.74%, 91.43% in NP and 87.38%, 88.21%, 85.82% in P Ch, respectively. In conclusion, vascular remodeling of uterine artery in pregnant goat (i) increased vascular resistance is due to increased sensitivity of α₁ adrenoceptor, (ii) augmented vasorelaxation to ACh due to endothelial activation of eNOS-NO-cGMP /COX-NO-cAMP pathways. We observed for the first time that vascular remodelling in pregnancy augmented the contraction and relaxation of uterine artery of goat is due to increased sensitivity of α₁-adrenergic receptor and EDRF.