Curr Health Sci J, vol. 37, no. 1, 2011

OANA-SORINA TICA⁽¹⁾, A. TICA⁽¹⁾, G. ADAM⁽²⁾, O. SIRBU⁽²⁾, S.MITROI⁽³⁾, C. BERCEANU⁽²⁾, M. MUNTEANU⁽²⁾

⁽¹⁾Department of Pharmacology, Faculty of Dental Medicine, University of Medicine and Pharmacy Craiova – Romania,
⁽²⁾Department of Obstetrics and Gynecology, Faculty of Medicine, University of Medicine and Pharmacy Craiova – RomAnia,
⁽³⁾Department of Epidemiology, University Hospital of Brasov – Romania

Abstract:

Myometrium is able to develop an intense spontaneous activity, without any external influences. However, endocrine environment can modulate, especially during pregnancy, the morphological and functional characteristics of the uterus. OBJECTIVES: The aim of this study is to quantify the impact of cyclic ovarian function on angiotensin II (AGII)-induced contraction of non-pregnant rat myometrium.  MATERIALS AND METHOD: The experiments were performed on rat uterine strips, females being previously included in three separated groups, conform on their ovarian cycle phases: estrum, diestrum and proestrum. The AGII-induced ocytocic effect was compared with the spontaneous activity, by measuring 4 parameters: a)the mean and b)the maximal amplitude of the oscillations, c)their frequency (number/10min.) and d)the area under the contraction curve, during 10 minutes. REZULTS: Spontaneous activity was characterized: 1)in estrum by: a)1,86g, b)2,17g, c)15/10min, d)239g.s.; 2)in diestrum by: a)1,63g, b)1,78g, c)11/10min, d)165g.s.; 3)in proestrum by: a)1,47g, b)1,53g, c)3/10min., d)40g.s. AGII increased the contractility (quantified through area under the curve) with: 462% in estrum, 358% in diestrum and 1.202% in proestrum. DISCUSSIONS:  Uterine spontaneous activity is maximal during estrum, this property being necessary for a rapid ascent of the sperm cells through female genital ways and for ovocytes capitation by the tubes. The minimal values were recorded in proestrum, the genital smooth muscle needing a rest period before its hyperactivity during estrum and, eventually, before a gestation. The diestrum was characterized by a medium intensity, together with a strong steadfastness of the uterine contractility. AGII-induced contractions followed very straightly the specific particularities of the spontaneous activity, excepting in proestrum, where its ocytocic effect was maximal. This last fact is the result of two phenomenon: 1)the automatic activity in  proestrum is very weak and 2)during this period only the spontaneous depolarizing mechanisms are strongly inhibited, but not the force generating systems. CONCLUSIONS: Spontaneous and AGII-induced uterine contractility are strongly dependent on cyclic ovarian secretion. Despite in humans, the rat myometrium is far more sensible to the oscillatory  hormonal plasma levels. It is no correlation between uterine contractility during different ovarian phases in human and rats, probable due to a completely different distribution and variability of the specific receptors.

Keywords: angiotensin II, myometrium, estrum, diestrum, proestrum

Corresponding: Assist. Prof. Oana Sorina Tica MD, PhD stud, Department of Pharmacology, Faculty of Dental Medicine, University of Medicine and Pharmacy Craiova, Petru Rares No. 2-4, Dolj, 200349, phone: +40-746.030.725; fax: +40-251.593.077; e-mail: oanabanica25@yahoo.com

DOI 10.12865/CHSJ.37.01.05 - Download PDF Ocytocic Effect OF Angiotensin II and the Cyclic Ovarian Function - Study on Rat Myometrium PDF