Three hours before OGTT rats were intraperitoneally administered vehicle (saline; n=4) or anti-MBG antibody (n=4), at a concentration which blocks 75% of circulating MBG, as described previously in detail. impairment of glucose tolerance, and higher levels of MBG as compared to that in normal pregnant rats. As compared to intact pregnant rats, NaCl supplementation of diabetic pregnant rats (drinking 1.8% NaCl during days 12-19 of pregnancy) was associated with an increase in systolic blood pressure, decreased fetal and placental weight, five-fold elevation of MBG excretion, and 42% inhibition of NKA in erythrocytes. In nonpregnant rats, in vivo pretreatment with anti-MBG antibody produced an exaggerated response of plasma levels of glucose and insulin in oral glucose tolerance test. These results suggest that MBG is a common factor in the pathogenesis of DM and preeclampsia, and that regulation of glucose tolerance may be one of the physiological functions of endogenous cardiotonic steroids. strong class=”kwd-title” Keywords: Diabetes mellitus, Glucose tolerance, Pregnancy, Preeclampsia, Hypertension, Salt-sensitivity, Na/K-ATPase, Marinobufagenin 1. INTRODUCTION Endogenous digitalis-like Na/K-ATPase (NKA) inhibitors, i.e., cardiotonic steroids (CTS), are implicated in the pathogenesis of NaCl-sensitve hypertension, diabetes mellitus (DM), and preeclampsia (PE) [1-3]. Clinical data indicate that impairment of glucose tolerance and DM both represent potential risk factors of PE [4,5]. In diabetics, perturbed NKA function is linked to impaired tissue insulin resistance, renal sodium retention, and development of hypertension, generation of reactive oxygen species, and cardiovascular remodeling [3,6,7]. Recently, we Rabbit Polyclonal to PPP2R3B demonstrated that in experimental rats and patients with type 1 and type 2 DM, inhibiton of NKA is accompanied by elevated levels of marinobufagnin (MBG), an endogenous bufadienolide CTS, a vasoconstrictor and a natriuretic [8,9]. Although PE is a major cause for maternal and fetal mortality and morbidity worldwide, its pathogenesis remains poorly understood. One of the factors contributing to the pathogenesis of PE are CTS [3,10,11]. Pregnancy is associated with renal sodium retention [12,13], a major stimulus for MBG production . In normal pregnancy, moderatly elevated levels of Sanggenone D MBG do not alter vascular tone [10,13]. In patients with PE and in pregnant rats with PE-like symptoms, however, levels of MBG become substantially elevated and accompany inhibition of the NKA [11,13,15]. Accordingly, in rats with PE-like symptoms, in vivo administration of anti-MBG antibody reduced blood pressure and restored activity of the sodium pump in vascular sarcolemma . Likewise, in patients with PE, anti-MBG antibody ex vivo restore activity of erythrocyte NKA . Since MBG represents a common link in the pathogenesis of PE and DM, we hypothesized that, in experimental pregnant rats with DM, Sanggenone D NaCl supplementation would facilitate excessive MBG production resulting in the development of PE-like symptoms. 2. METHODS 2.1. Experimental protocol The study protocol was approved by the Research Council of Sechenov Institute of Evolutionary Physiology and Biochemistry, St. Petersburg, Russia in accordance with the rules and regulations of the National Institutes of Health, Bethesda, MD, USA. Type 2 (non-insulin-dependent) DM was produced by a single subcutaneous injection of 65 mg/kg streptozotocin (STZ) to 48 neonatal rats as described previously . Control rats received a single intraperitoneal injection of Sanggenone D a vehicle, citrate-buffered saline (pH 5.5)(n=24). Rats with type 2 DM exhibited moderate elevation of plasma glucose levels and substantial increases in the plasma levels of insulin (Results). Ten weeks following administration of STZ or vehicle, animals were divided into the following groups (n = 12 per groups): nondiabetic virgin rats, diabetic virgin rats, nondiabetic pregnant rats, nondiabetic pregnant rats supplemented with NaCl, diabetic pregnant rats, and diabetic pregnant rat supplemented with NaCl. Pregnancy was induced in ten-week old diabetic and nondiabetic rats. Day 1 of pregnancy was established when spermatozoa were found in morning vaginal smears. Nonpregnant rats were selected randomly through the estrous cycle and paired with pregnant ones. All animals were housed under controlled light (6 AMC6 PM) and temperature (22C) and were fed a normal diet ad libitum. Control pregnant rats had tap water for the duration of the experiment. NaCl-supplemented rats drank 1.8% NaCl solution for 7 days, during days 12-19 of gestation. Systolic blood.