Abstract
Aims.Plasma renin concentration (PRC) is a log-linear function of sodium intake (NaI) in dogs (Kjølby & Bie, 2008). We tested the hypotheses that (i) this also is true for rats, (ii) this also is true for GFR and blood pressure, and (iii) the parameters change by chronic infusion of metoprolol.
Methods. Chronically catheterized rats were studied 5 d after surgery and more than 3 days of low-salt diet. Sodium intake was varied from 0.07 to16 mmol/kg/d by infusion. PRC blood samples were obtained at the end of the night periods. Mean arterial blood pressure (MABP) was sampled 2 x 10 h/d, and glomerular filtration rate (GFR) measured by inulin clearance. Metoprolol (1 mg/kg/h) was administered i.v. to block β1 adrenergic receptors.
Results. Over the ~200 fold range of NaI, PRC, MABP and GFR were linearly related to log(NaI). In control experiments, relations were PRC = -8.2 log(NaI) + 19.6; MABP = 4.0 log(NaI) + 96, and GFR = 1.2 log(NaI) + 8.8. Metoprolol reduced MABP significantly (p<0.01) but did not change the slope, MABP = 5.8 log(NaI) + 87. In contrast, the PRC-NaI relation (PRC = -8.7 log(NaI) +19.6) was indistinguishable from control.
Conclusion. The results confirm in the rat that PRC is a log-linear function of NaI and extend the concept to MABP and GFR. Surprisingly β1 adrenoceptors do not seem importantly in-volved in steady state renin secretion, or alternatively, their function is quantitatively replaced by the effect of hypotension.
Reference. Kjølby M. & Bie P. Am.J.Physiol.Regul.Integr.Comp.Physiol. 294:R17-25, 2008.
Methods. Chronically catheterized rats were studied 5 d after surgery and more than 3 days of low-salt diet. Sodium intake was varied from 0.07 to16 mmol/kg/d by infusion. PRC blood samples were obtained at the end of the night periods. Mean arterial blood pressure (MABP) was sampled 2 x 10 h/d, and glomerular filtration rate (GFR) measured by inulin clearance. Metoprolol (1 mg/kg/h) was administered i.v. to block β1 adrenergic receptors.
Results. Over the ~200 fold range of NaI, PRC, MABP and GFR were linearly related to log(NaI). In control experiments, relations were PRC = -8.2 log(NaI) + 19.6; MABP = 4.0 log(NaI) + 96, and GFR = 1.2 log(NaI) + 8.8. Metoprolol reduced MABP significantly (p<0.01) but did not change the slope, MABP = 5.8 log(NaI) + 87. In contrast, the PRC-NaI relation (PRC = -8.7 log(NaI) +19.6) was indistinguishable from control.
Conclusion. The results confirm in the rat that PRC is a log-linear function of NaI and extend the concept to MABP and GFR. Surprisingly β1 adrenoceptors do not seem importantly in-volved in steady state renin secretion, or alternatively, their function is quantitatively replaced by the effect of hypotension.
Reference. Kjølby M. & Bie P. Am.J.Physiol.Regul.Integr.Comp.Physiol. 294:R17-25, 2008.
| Original language | English |
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| Publication date | 1. Oct 2011 |
| Publication status | Published - 1. Oct 2011 |
| Event | ECCR (European Council of Cardiovascular Research) 16th annual meeting - Nice, France Duration: 30. Sept 2011 → 2. Oct 2011 |
Conference
| Conference | ECCR (European Council of Cardiovascular Research) 16th annual meeting |
|---|---|
| Country/Territory | France |
| City | Nice |
| Period | 30/09/2011 → 02/10/2011 |