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Biomedical subjects

R G Park

Publications and source records attributed to R G Park.

7 recordsLinked to original sources
PubMed1989

Renal denervation does not prevent dehydration-induced natriuresis in sheep.

Normal sheep or sheep in which the renal nerves had been extirpated were deprived of water for 2 days in order to determine whether changes in renal nerve activity contribute to natriuresis during water deprivation. Both groups of sheep showed a considerable natriuresis throughout the period of water deprivation and increases in plasma osmolality and plasma Na concentration. Renal denervation, as indicated by the absence of catecholamine fluorescence in kidney sections, was extensive. Previous experiments have suggested cerebral involvement in the induction of dehydration-induced natriuresis. The present results indicate that the efferent pathway mediating this cerebral influence on renal sodium excretion does not involve the renal nerves, suggesting a hormonal mechanism as the likely pathway.

Animals↗
PubMed1986

Augmented plasma renin levels in dehydrated sheep with periventricular lesions.

Ablation of tissue in the midline anterior wall of the third ventricle (AV3V) of sheep did not consistently alter baseline plasma renin concentration (PRC) in water replete animals, but caused a greatly augmented increase in PRC in response to water deprivation. PRC might increase in these sheep in order to maintain blood pressure, however it is possible that a central inhibitory influence on renal renin release, operative during dehydration, is disrupted by AV3V-lesions.

Animals↗
PubMed1986

Ablation of subfornical organ does not prevent angiotensin-induced water drinking in sheep.

The subfornical organ (SFO) and surrounding periventricular tissue were ablated in sheep. Such a lesion did not significantly reduce water drinking in response to intracarotid, intravenous, or intracerebroventricular infusions of [Val5]angiotensin II amide (ANG II) but caused reduced intake of water in response to intracarotid infusion of hypertonic saline. The dipsogenic response of these sheep to water deprivation for 3 days was similar to that of normal sheep subjected to water deprivation. Although the results are not conclusive in excluding the SFO from having a role in ANG II-induced drinking, they show that there are receptors outside the SFO sensitive to blood-borne ANG II that are involved in water drinking in sheep. The results also show that tissue in the SFO or its surroundings may be involved in drinking caused by acute hypertonicity.

Angiotensin II↗
PubMed1986

Volume influences on thirst and vasopressin secretion in dehydrated sheep.

The contribution of extracellular fluid volume (ECFV) to water consumption and plasma vasopressin concentration (PAVP) after water deprivation for 52 h was examined in sheep. Intravenous infusion of isotonic NaCl, equivalent to either estimated ECFV loss or total body water loss, significantly reduced water intake by 37% when water was offered 3 h after infusion but not when water was offered 1 h after infusion. Plasma osmolality (POsm) was reduced after 3 h. Infusion of 200 mM NaCl, which maintained POsm, decreased water consumption by the same degree as isotonic NaCl infusion. Thus large decreases in POsm had no effect on water intake in this experimental protocol. Lack of inhibition of drinking 1 h after infusion suggests that the decrease observed after 3 h may have been mediated by receptors in the interstitial fluid (ISF) compartment and not the intravascular compartment. PAVP was reduced 3 h after infusion of NaCl but not at 1 or 2 h after infusion. POsm was also decreased at 3 h. Thus reduction of PAVP by NaCl infusion may have been caused by either ISF or intracellular fluid volume expansion.

Animals↗
PubMed1985

Natriuresis induced by arginine vasopressin infusion in sheep.

The aim of this study was to investigate whether arginine vasopressin (AVP) is natriuretic in sheep at plasma concentrations comparable to those induced by water deprivation. AVP was infused intravenously at 0.1, 0.2, and 0.5 microgram/h for 24-48 h in sheep allowed free access to water. Infusion of AVP at 0.1 microgram/h did not alter renal Na output, whereas infusion of AVP at both 0.2 and 0.5 microgram/h significantly increased daily output of Na in urine. Significant natriuresis did not occur until 3.5 h after the start of AVP infusion at 0.2 microgram/h. Plasma AVP levels induced by these infusions were 9.8 +/- 1.6 (0.1 microgram/h AVP), 21.9 +/- 7.7 (0.2 microgram/h AVP), and 32.5 +/- 9.0 pg/ml (0.5 microgram/h AVP) after 24 h. These concentrations are within the range found in sheep deprived of water for 3 days. Hypophysectomy abolished increases in plasma AVP concentration but not natriuresis in response to water deprivation. This suggests that increased plasma AVP concentration does not play an essential role in the mechanisms subserving dehydration-induced natriuresis.

Animals↗
PubMed1978

Psoriasis.

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Adolescent↗