Partial renal ischemia elicits heterogeneous control of renal sympathetic nerve activity to ischemic and nonischemic regions of the kidney

Abstract

We tested the hypothesis that renal sympathetic nerve activity (RSNA) to the ischemic and nonischemic regions responded differently during partial ischemia of the kidney in pentobarbital-anesthetized cats. The renal artery divides into two branches at the front of the renal hilus: one branch perfuses predominantly the dorsal half of the kidney, and the other perfuses its ventral half. We identified the innervated area of a renal nerve bundle by supramaximal electrical stimulation and subsequently determined the changes in RSNA in response to occlusion of either renal arterial branch for 3 min. RSNA to the nonischemic region of the kidney gradually decreased by 23 +/- 4% during partial renal ischemia, whereas RSNA to the ischemic region of the same kidney showed no significant change. Crushing either all renal nerve bundles or only the renal nerve bundles terminated to the ischemic region abolished the decrease in RSNA to the nonischemic region. Furthermore, intra-arterial administration of a prostaglandin synthesis inhibitor (meclofenamate, 4 mg/kg) abolished the decrease in RSNA to the nonischemic region of the kidney. Following spinal transection at the level of T7, the inhibitory response in RSNA to the nonischemic region disappeared, whereas the RSNA to the ischemic region was markedly augmented by 47 +/- 17%. Thus it is likely that renal chemoreceptors activated during renal partial ischemia elicit heterogeneous control of renal sympathetic outflows to the ischemic and nonischemic regions of the same kidney, which may be determined by a net output between the supraspinal inhibitory and spinal excitatory reflexes.

Stimulation of brain mast cells by compound 48/80, a histamine liberator, evokes renin and vasopressin release in dogs

“…Such enhancements in ADH and plasma NE responses have been seen in spaceflight (45) and in hindlimbunloaded animals (49,64). Indeed, mechano-and chemosensitive information transmitted from the kidneys to the paraventricular nucleus (PVN) of the hypothalamus via the renal afferent nerves has been shown to contribute to the modulation of ADH release (14,58,60). Fig.…”

“…Histamine and its receptors are highly concentrated within the hypothalamus (4,6,40,57,59), and various types of stress induce significant alterations in both histamine synthesis and its concentration in several brain regions (5,57,59,63). Renin secretion is activated via the hypothalamic-sympathetic outflow during various forms of stress (1,14,60) and also during cardiovascular dysfunction (3,13,26,33,35,36,58). Antidiuretic hormone (ADH), along with the renin-angiotensin system, is of great importance in regulating the defenses against both stress and cardiovascular dysfunction (57).…”

Unraveling the basic principles

“…It appears therefore likely that morphogenesis in the developing kidney and restoration of mature kidney function after ischemic renal injury is established through a similar genetic program. Recent findings indicate that partial renal ischemia elicits a heterogeneous efferent sympathetic nerve activity to the ischemic and nonischemic regions of the same kidney (19). One is therefore tempted to speculate that heterogeneities in renal sympathetic outflow may underlie, at least in part, the spatially and temporally restricted pattern of nephrogenic proteins in the postischemic kidney.…”