Ontogeny of the renal urotensin II system in the rat

Abstract

Urotensin II (UII), a peptide hormone which influences glomerular filtration rate and urine concentration, and its receptor, UT, are expressed in the adult rat kidney. The ability of the kidney to reabsorb sodium and water starts to develop in utero and matures during early postnatal life in the rat, yet little is known about the ontogeny of the renal UII system. This study mapped renal expression of the urotensin system during the fetal and postnatal periods and determined renal activity of UII in the immature rat. Urotensin II peptide and mRNA were present in Sprague-Dawley (SD) rat metanephroi from the earliest stage examined, embyonic day 19 (E19; rat gestation 22 days); levels increased to peak at 4 weeks of age. In contrast, UT protein and mRNA expression declined rapidly between E19 and birth and remained at a similar level postnatally. Infusion of rat UII [6-60 pmol min −1 (100 g body weight)−1 ] or rat urotensinrelated peptide [6 pmol min −1 (100 g body weight)−1 ] in anaesthetized 4-week-old SD rats had no influence on measured renal parameters; however, infusion of UT antagonist, SB-706375 (0.01 mg kg −1 min −1 ), provoked a pronounced diuresis [vehicle 23.5 ± 1.9 versus antagonist 75.3 ± 12.5 μl min −1 (100 g body weight) −1 ; P < 0.001] and natriuresis, accompanied by modest increases in effective renal blood flow and glomerular filtration rate [vehicle 0.4 ± 0.1 versus antagonist 1.1 ± 0.2 ml min −1 (100 g body weight) −1 ; P < 0.0001] and a significant increase in fractional sodium excretion. These results indicate that the endogenous rat UII system may influence renal sodium and water excretion before the onset of full urine concentrating capacity in the SD rat.

Pressor and renal regional hemodynamic effects of urotensin II in neonatal pigs

“…An examination of the ontogenetic pattern of UII and UTR expression in rat kidney has also revealed regional variability in UII and UTR expression from embryonic day 19 to 4 weeks after birth (Forty & Ashton 2012). However, unlike in adult, rat UII (rUII) did not alter renal hemodynamics in young (4-week-old) rats (Forty & Ashton 2012).…”

The Urotensin System Is Up-Regulated in the Pre-Hypertensive Spontaneously Hypertensive Rat

“…We have reported recently that the urotensin system exerts a tonic influence on GFR and sodium and water excretion in 4 week-old Sprague Dawley rats [19]. Consequently, in view of the enhanced renal sensitivity to UII that we observed in adult SHR [13], we hypothesise that the urotensin system contributes to the lower GFR of the young, pre-hypertensive SHR.…”

“…anaesthetised 4-5 week-old WKY rats and SHRs were surgically prepared for renal clearance measurements [19]. A priming dose of renal clearance markers was administered via a jugular catheter (2 μCi 3 H inulin [Perkin-Elmer, Monza, Italy] and 12 mg para-aminohippuric acid [PAH] in 0.2 ml 0.154 mol/L NaCl).…”

Renal Urotensin II System Plays Roles in the Regulation of Blood Pressure in Dahl Salt-Resistant Rat

“…Many studies showed that elevated plasma level of UII and increased expression of UII and UT can be identified in the tissues of numerous diseased conditions, including hypertension, preeclampsia, atherosclerosis, heart failure, pulmonary hypertension, diabetes, renal failure, and various metabolic syndromes [7, 8]. It is reported that UII is upregulated in the spontaneously hypertensive rat [9], which means that UII is mainly a vasoconstrictor [9, 10]; however, recent studies also showed that UII has vasodilatory effect. An example demonstrating the dilatory function of UII is that patients on hemodialysis with lower blood pressure were found with elevated UII level [11].…”

“…Besides its constricted or dilated function on vessels, it is reported that UII has been shown to regulate epithelial sodium transport. In secretory tissues, such as opercular skin, UII inhibited active sodium and chloride transport [9]. These observations demonstrate that UII can directly affect epithelial ion transport in fish and influence body fluid homeostasis [21].…”