In-utero cold stress causes elevation of blood pressure via impaired vascular dopamine D1 receptor in offspring

Exposure of the Gestating Mother to Sympathetic Stress Modifies the Cardiovascular Function of the Progeny in Male Rats

BACKGROUND

Sympathetic stress stimulates norepinephrine (NE) release from sympathetic nerves. During pregnancy, it modifies the fetal environment, increases NE to the fetus through the placental NE transporter, and affects adult physiological functions. Gestating rats were exposed to stress, and then the heart function and sensitivity to in vivo adrenergic stimulation were studied in male progeny.

METHODS

Pregnant Sprague-Dawley rats were exposed to cold stress (4 °C/3 h/day); rats' male progeny were euthanized at 20 and 60 days old, and their hearts were used to determine the β-adrenergic receptor (βAR) (radioligand binding) and NE concentration. The in vivo arterial pressure response to isoproterenol (ISO, 1 mg/kg weight/day/10 days) was monitored in real time (microchip in the descending aorta).

RESULTS

Stressed male progeny presented no differences in ventricular weight, the cardiac NE was lower, and high corticosterone plasma levels were recorded at 20 and 60 days old. The relative abundance of β1 adrenergic receptors decreased by 36% and 45%, respectively (p < 0.01), determined by Western blot analysis without changes in β2 adrenergic receptors. A decrease in the ratio between β1/β2 receptors was found. Displacement of ³H-dihydroalprenolol (DHA) from a membrane fraction with propranolol (β antagonist), atenolol (β1 antagonist), or zinterol (β2 agonist) shows decreased affinity but no changes in the β-adrenergic receptor number. In vivo exposure to ISO to induce a β-adrenergic overload provoked death in 50% of stressed males by day 3 of ISO treatment.

CONCLUSION

These data suggest permanent changes to the heart's adrenergic response after rat progeny were stressed in the uterus.

Dopamine outside the brain: The eye, cardiovascular system and endocrine pancreas

Dopamine (DA) and DA receptors (DR) have been extensively studied in the central nervous system (CNS), but their role in the periphery is still poorly understood. Here we summarize data on DA and DRs in the eye, cardiovascular system and endocrine pancreas, three districts where DA and DA-related drugs have been studied and the expression of DR documented. In the eye, DA modulates ciliary blood flow and aqueous production, which impacts on intraocular pressure and glaucoma. In the cardiovascular system, DA increases blood pressure and heart activity, mostly through a stimulation of adrenoceptors, and induces vasodilatation in the renal circulation, possibly through D1R stimulation. In pancreatic islets, beta cells store DA and co-release it with insulin. D1R is mainly expressed in beta cells, where it stimulates insulin release, while D2R is expressed in both beta and delta cells (in the latter at higher level), where it inhibits, respectively, insulin and somatostatin release. The formation of D2R-somatostatin receptor 5 heteromers (documented in the CNS), might add complexity to the system. DA may exert both direct autocrine effects on beta cells, and indirect paracrine effects through delta cells and somatostatin. Bromocriptine, an FDA approved drug for diabetes, endowed with both D1R (antagonistic) and D2R (agonistic) actions, may exert complex effects, resulting from the integration of direct effects on beta cells and paracrine effects from delta cells. A full comprehension of peripheral DA signaling deserves further studies that may generate innovative therapeutic drugs to manage conditions such as glaucoma, cardiovascular diseases and diabetes.