title: Effect of monensin and a protonophore on protein degradation, peptide accumulation, and deamination by mixed ruminal microorganisms in vitro.
abstract: Mixed ruminal bacteria (80 mg N/liter) degraded casein and soluble soy protein rapidly (.68 and .72 mg N/[liter.min], respectively), but ammonia was produced at a slower rate (.08 and .10 mg N/[liter.min], respectively). Because there was little increase in cell protein, ammonia production could not account for all the degraded protein. Large quantities of non-ammonia, non-protein nitrogen (NAN-NPN) accumulated, and this NAN-NPN reacted more strongly (2- to 14-fold) with ninhydrin after it was treated with 6 N HCl (110 degrees C, 24 h) or pronase E. Even after 96 h of incubation, 10% of the protein N was still found in the NAN-NPN pool. Monensin had little effect on protein degradation, but it caused a large decrease in ammonia production (P less than .05) and an increase in NAN-NPN (P less than .05). These results indicated that significant quantities of peptide N could not be degraded by ruminal microorganisms and that monensin could increase peptide flow from the rumen. Because 3,3',4',5-tetrachlorosalicylanide, a protonophore that inhibits both Gram-positive and Gram-negative bacteria, did not cause a greater decrease (P greater than .05) in ammonia than monensin, an ionophore that is primarily effective against Gram-positive bacteria, it seemed that the "protein sparing" of monensin could largely be explained by its inhibition of Gram-positive bacteria.
authors.affiliation: Dept. Anim. Sci., Cornell Univ., Ithaca, NY 14853.
authors.forename: G J
authors.initials: GJ
authors.lastname: Chen
authors.forename: J B
authors.initials: JB
authors.lastname: Russell
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D003641:Deamination; D005260:Female; D008985:Monensin / Q000494:pharmacology*; D010455:Peptides / Q000378:metabolism; D014674:Plant Proteins, Dietary / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000494:pharmacology; D012417:Rumen / Q000382:microbiology*; D012458:Salicylanilides / Q000494:pharmacology*; D030262:Soybean Proteins; D013025:Glycine max
chemical_list: D002364:Caseins; D010455:Peptides; D014674:Plant Proteins, Dietary; D011506:Proteins; D012458:Salicylanilides; D030262:Soybean Proteins; D000641:Ammonia; D008985:Monensin; D006180:Proton-Translocating ATPases; C003390:3,3',4',5-tetrachlorosalicylanilide