Roles of eating, rumination, and arterial pressure in determination of the circadian rhythm of renal blood flow in sheep1

Abstract

To assess the roles of feeding behavior (eating and rumination) and systemic arterial pressure (SAP) on determination of the circadian rhythm of renal blood flow (RBF), 20 sheep fitted with ultrasonic flow-metering probes around both renal arteries and a submandibular balloon to monitor jaw movements (6 of them with a telemetry measurement system into the carotid artery for SAP recording), were successively assigned to 6 feeding patterns: once daily in the morning (0900 to 1100 h), afternoon (1700 to 1900 h), or evening (1900 to 2100 h); twice daily at 0900 to 1100 h and 1700 to 1900 h; ad libitum (food renewed each 2 h); and fasting (40 h). All protocols were carried out in autumn-winter, and the fasting pattern was repeated in spring-summer to evaluate the effect of the daylight length on RBF. In the once-daily feeding patterns, a rapid increase in RBF (P < 0.05 vs. 1-h prefeeding mean values) subsequent to the onset of meals was observed, followed by a progressive increase (P < 0.05), reaching a maximum 4 to 6 h after the beginning of eating, and a subsequent gradual decline until the next meal [differences vs. prefeeding values were no longer significant after 11 h (morning pattern), 13 h (afternoon pattern), and 15 h (evening pattern) from the beginning of eating]. In the twice-daily feeding pattern, each meal was also followed by an increase in RBF (P < 0.05 vs. prefeeding values), reaching a maximum 3 to 5 h after the onset of meals, and a posterior decline [differences vs. prefeeding values were no longer significant after 8 h (morning meal) and 5 h (afternoon meal) from the beginning of eating]. In the ad libitum feeding, no apparent rhythm in RBF was found. During fasting, a progressive reduction of RBF was observed from 2 h after the beginning of fasting (P < 0.05 vs. the mean value of the first fasting hour), with a slight rebound (P < 0.05) lasting several hours from approximately 0700 h in autumn-winter and approximately 0500 h in spring-summer. No change in the RBF profile was observed in association with rumination. Except during meals, no correlation was found between RBF and SAP. A detailed description of RBF and SAP recordings is presented. In conclusion, results showed a circadian rhythm of RBF determined by eating behavior, but not by rumination, that was independent of blood pressure and that seemed superimposed on a primary lighting-cycle-dependent RBF rhythm.

Effects of Birth Weight and Feeding System on Fattening Performance and Feeding Behaviour of Karayaka Male Lambs

“…These results indicates that lambs may be adapted their feeding behaviour to the kind of diet they receive, as reported by Abijaoudé et al (2000) and Keskin et al (2005). Because rumination is considered as a second meal, inducing a regain in digestive and absorptive processes without new ingested food (Tebot et al, 2009), it is clear why it did not influence eating activity but not drinking activity. The some factors, such as diet composition and the amount of dry matter intake can affect drinking behaviour (Keskin et al, 2005).…”

The effect of intravenous insulin infusion on renal blood flow in conscious sheep is partially mediated by nitric oxide but not by prostaglandins1

“…An insulin-induced vasodilatatory response has been reported in different species (Muniyappa et al, 2007), and plasma insulin increases after meals in ruminants (Trenkle, 1978;Mineo et al, 1990). In a sheep model, we observed an increase in RBF after meals, independent of blood pressure (Denis et al, 2004;Tebot et al, 2009). Consequently, a causal relationship between insuhn and the meal-associated RBF changes could be proposed.…”

“…; Ketofen, Mérial, Lyon, France) for 3 d. No postsurgical disturbances were observed. When optimal ultrasonic signals were obtained (1 wk after surgery, required for probe encapsulation), 4 of the sheep were fitted with a telemetry measurement system (model TL11M3-D70-CCP Physiotel Transmitter, Data Sciences International, St. Paul, MN) into 1 carotid artery (same anesthetic protocol) for systemic arterial pressure (SAP) monitoring, as also described previously (Tebot et al, 2009). This monitoring was necessary because the autonomie nervous system was reported to take part in the skeletal muscle vasomotion induced by insulin (Muniyappa et al, 2007), and variations in renal hemodynamics were partly attributed to changes in arterial pressure (Millar-Craig et al, 1978).…”

“…I. The first protocol was designed to determine the plasma insulin changes during the reported (Tebot et al, 2009) RBF increase associated with meals, and to evaluate the effect of insulin infusions on RBF. On 3 alternate days, RBF and SAP were continuously recorded between 0800 and 1800 h, and blood samples were taken every 30 min.…”

“…sodium thiopentone (15 mg/kg of BW; Nesdonal, Mérial, Lyon, France) and maintained with isofiurane (0.5 to 2%; Aerrane, Baxter, Maurepas, France) in O2 (6 L/min). Transit-time ultr2isonic ñowmetering probes (4 mm, R-series, Transonic Systems, Ithaca, NY) were bilaterally implanted around the renal arteries for continuous measurement of RBF, as described previously (Tebot et al, 2009). After surgery.…”