Influence of substrate and/or neurohormonal mimic on in vitro pancreatic enzyme release from calves postruminally infused with partially hydrolyzed starch and/or casein1

Abstract

Our objectives were to determine the effects of neuroendocrine challenge and substrates on in vitro alpha-amylase and trypsin release in pancreatic tissue collected from Holstein calves (n = 24; 88 +/- 3 kg) abomasally infused for 10 d with tap water (control), partially hydrolyzed starch (SH; 4 g/[kg of BW x d]) and/ or casein (0.6 g/[kg of BW x d]). The caudal portion of the pancreas was removed, rinsed with ice-cold saline, cut into approximately 2 x 2-mm segments, and incubated in oxygenated Krebs Ringer bicarbonate buffer containing no substrate (control), glucose, amino acids, or VFA at 39 degrees C. After 60 min of incubation, neurohormonal mimics (none; control), carbachol (acetylcholine analog; 10 microM final), or caerulein (cholecystokinin mimic; 100 nM final) were added to the flasks and tissue was incubated for 60 min. Pancreatic tissue concentrations and in vitro release of alpha-amylase and trypsin decreased (P < 0.001) in calves abomasally infused with SH. Carbachol increased (P < 0.10) alpha-amylase and trypsin release in tissue collected from all calves. An effect of caerulein to increase alpha-amylase release (P < 0.10) was only observed with prior exposure to abomasal casein infusion in vivo or with simultaneous incubation with amino acids in vitro. Caerulein increased (P < 0.10) trypsin release in tissue collected from all calves except for those receiving SH + casein. Glucose decreased (P < 0.10) alpha-amylase release from pancreatic tissue collected from calves receiving abomasal control and casein treatments. Amino acids decreased (P < 0.10) alpha-amylase and trypsin release from pancreatic tissue collected from calves receiving the abomasal control treatment. Glucose, amino acids, and VFA decreased (P < 0.10) trypsin release from tissue collected from calves receiving abomasal SH. These data indicate that carbachol can stimulate pancreatic enzyme release in vitro. Caerulein, however, is only effective in stimulating in vitro pancreatic enzyme release in tissue from calves with an increased postruminal protein supply or in tissue incubated with amino acids. The results indicate that postruminal and local nutrients might be important in altering the responsiveness to a neuroendocrine challenge and could be an important regulatory event involved with dietary adaptation in ruminants.

Duodenal supply of glutamate and casein both improve intestinal starch digestion in cattle but by apparently different mechanisms1

“…Increased dietary protein has been associated with increased plasma CCK in both nonruminants (Konturek et al, 1973;Nishi et al, 2003;Veldhorst et al, 2008) and ruminants (Furuse et al, 1992). Swanson et al (2003) observed direct responses of cattle pancreatic tissues when incubated with caerulein, a CCK analog. Circulating concentrations of CCK were not strongly affected by treatment in Exp.…”

“…We interpret the increase in ethanol-soluble starch flow and lack of response in small intestinal starch digestion in response to EAA to suggest that luminal hydrolysis of starch via pancreatic α-amylase was increased by EAA, but small intestinal starch digestion was limited by hydrolysis of small-chain oligosaccharides by α-glycohydrolases. Swanson et al (2003) noted that pancreatic tissue from cattle with greater postruminal supplementation of casein had increased responsiveness to CCK and acetylcholine agonists. Hara et al (2001) reported that nonessential AA play an integral role in secretion of α-amylase in rats, and specific nonessential AA can be essential for secretion of α-glycohydrolases by the intestinal epithelium (Schroder et al, 1995;Horvath et al, 1996;Weiss et al, 1999).…”

“…1. Nonetheless, some authors (Morisset et al, 2003;Konturek et al, 2003;Swanson et al, 2003;Zabielski, 2003) have questioned the classic hormone theory associated with CCK, and a preponderance of recent findings suggest that the parasympathetic nervous system is often involved in mediating CCK's stimulatory effect. Direct reports (Benson and Reynolds, 2001) that hepatic removal of CCK in cattle is related to hepatic metabolism further questions CCK's role as a precise chemical messenger to the pancreas in cattle.…”

“…Direct reports (Benson and Reynolds, 2001) that hepatic removal of CCK in cattle is related to hepatic metabolism further questions CCK's role as a precise chemical messenger to the pancreas in cattle. Swanson et al (2003) reported that responses of cattle pancreatic tissue to a CCK analog was dynamic and occurred only in tissues harvested from cattle that had received greater postruminal protein supplies. Clearly, a complete description of CCK's relationship to small intestinal starch digestion in cattle is yet to be elucidated.…”

Influence of rumen escape starch on pancreatic exocrine secretion of goats

“…Several researchers have shown that post‐ruminal or intravenous infusions of α‐amylase products result in decreases of expression (Swanson et al., 2000, 2002a, 2003) and secretion (Call et al., 1975; Walker and Harmon, 1995; Swanson et al., 2002b, 2004) of pancreatic α‐amylase in cattle and sheep. It was hypothesized that excessive RES inhibiting pancreatic α‐amylase secretion may be related to the accumulation of α‐amylase products in the small intestine and in the blood.…”