Hemodynamic characterization of hypertension induced by chronic intrarenal or intravenous infusion of norepinephrine in conscious rats.

We tested methods for delivery of drugs to the renal medulla of anesthetized rabbits. Outer medullary infusion (OMI) of norepinephrine (300 ng ⋅ kg−1 ⋅ min−1), using acutely or chronically positioned catheters, reduced both cortical (CBF; 15%) and medullary perfusion (MBF; 23–31%). Inner medullary infusion (IMI) did not affect renal hemodynamics, whereas intravenous infusion reduced CBF (15%) without changes in MBF. During OMI of [3H]norepinephrine, much of the radiolabel (∼40% with chronically positioned catheters) spilled over systemically. Nevertheless, autoradiographic analysis showed the concentration of radiolabel was about fourfold greater in the infused medulla than the cortex. In contrast, during IMI, only ∼5% of the infused radiolabel spilled over into the systemic circulation and ∼64% was excreted by the infused kidney. The resultant intrarenal levels of radiolabel were considerably less with IMI compared with OMI. In rabbits, OMI therefore provides a useful method for targeting agents to the renal medulla, but given the considerable systemic spillover with OMI, its utility is probably limited to substances that are rapidly degraded in vivo.

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Regulation of plasma arginine vasotocin in conscious water-deprived domestic fowl

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.250.4.r658 ◽

1986 ◽

Vol 250 (4) ◽

pp. R658-R664 ◽

Cited By ~ 3

Author(s):

J. N. Stallone ◽

E. J. Braun

Keyword(s):

Antidiuretic Hormone ◽

Fluid Balance ◽

Intravenous Infusion ◽

Domestic Fowl ◽

Water Deprivation ◽

Extracellular Volume ◽

Plasma Osmolality ◽

Arginine Vasotocin ◽

Plasma Arginine

Radioimmunoassay methods were employed to quantitatively characterize secretion of the avian antidiuretic hormone [arginine vasotocin (AVT)] by the hypothalamo-neurohypophyseal system (HNS) of the conscious domestic fowl in response to chronic dehydration. Water deprivation permitted characterization of AVT secretion in response to the combined stimuli of extracellular hyperosmolality and hypovolemia; the subsequent repletion of extracellular volume permitted separation of potential osmotic and volemic factors involved in the regulation of AVT secretion. In normally hydrated birds, plasma AVT (PAVT) and plasma osmolality (Posm) averaged 2.2 +/- 0.3 microU/ml (10.5 +/- 1.4 pg/ml) and 309.3 +/- 0.7 mosmol/kg H2O, respectively (means +/- SE). With water deprivation, PAVT and Posm of the birds increased in parallel in a curvilinear manner to maxima of 13.1 +/- 0.6 microU/ml (62.4 +/- 2.9 pg/ml) and 346.6 +/- 2.0 mosmol/kg H2O, respectively, at 96 h of dehydration. The isosmotic repletion of extracellular volume at 96 h by acute intravenous infusion failed to alter 96-h PAVT values. The results indicate that AVT secretion is closely linked to the state of hydration during negative fluid balance in the domestic fowl. Analysis of the data indicated that increases in PAVT that occur with dehydration are mediated primarily by extracellular hyperosmolality and that the HNS of the domestic fowl is relatively insensitive to the simultaneous hypovolemia incurred with fluid deprivation.

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