Cation concentration in skeletal muscle of paretic and nonparetic cows
Kowalczyk, D.F.; Mayer, G.P.
American Journal of Veterinary Research 33(4): 751-757
1972
ISSN/ISBN: 0002-9645 PMID: 5017868 Document Number: 56724
Biopsy samples were taken from the semitendinosus muscle of 12 non-parturient cows, from 8 paretic parturient cows during paresis and after recovery, and from 8 normal recently-calved cows. Ca, Mg, K and Na concentrations were determined in muscle and plasma, and dry matter content of the muscle tissue was determined. Parturition was associated with reduced muscle potassium concentration which was more pronounced in the paretic cows. Although recovery from paresis was associated with increase in muscle potassium, the content remained less than that of non-partuient and control cows. The calcium concentration of musle of paretic cows was not significantly less than that for parturient control cows, despite more severe hypocalcaemia in the paretic cows. The cellular concentration of calcium in hypocalcaemic paretic cows was adequate for muscle contraction. The increased Na and decreased K concentration of paretic muscle suggests that hypocalcaemia may have increased the permeability of the cell membrane to these cations. An increase in permeability could reduce the potential difference across the cell membrane and alter cellular excitability. Initially, reduction of the transmembrane potential would lead to cellular hyperexcitability. Further reduction of the transmembrane potential might lead to inexcitability (paresis).