Glycogen in leukocytes from bovine blood and milk.

Glycogen content was determined quantitatively by the Anthrone reagent method in leukocytes obtained from blood and milk of five cows. Distribution of glycogen in leukocytes was studied by microscopic examination of slides stained by Periodic acid-Schiff (PAS) reaction. Blood glucose concentrations were investigated in these animals by standard procedures. In two of five cows both blood glucose levels and blood leukocyte glycogen levels on the same day were determined for six consecutive days. One hundred and two blood leukocyte samples from five cows had a mean glycogen content of 1.32 +/- 0.04 (S.E.) mg/10(9) WBC, and 6.11 +/- 0.17 (S.E.) mg/10(9) PMNs. Leukocyte preparations from 80 samples of milk comprising 97 to 98% PMNs contained 3.81 +/- 0.18 (S.E.) mg glycogen/10(9) milk leukocytes. In PAS preparations of blood and milk leukocytes glycogen was found almost exclusively in PMNs. Glycogen granules, present frequently in PMNs and occasionally in monocytes and large lymphocytes from blood, were not observed in those from milk. The glycogen level in milk leukocytes was significantly lower (P = <0.01) than that of the blood PMNs in every cow, and the overall mean difference between levels for milk leukocytes and blood PMNs was highly significant (P = <0.001). Mean blood glucose concentration in the five cows was 44.46 +/- 0.66 (S.E.) mg%. There was no significant relationship between blood glucose and blood leukocyte glycogen levels in the five corresponding cows; nor between blood glucose and blood PMN glycogen levels on the same day in either of two cows investigated. Leukocyte preparations from milk samples obtained on the second day following intramammary infusion of endotoxin consistently contained markedly less glycogen than the leukocyte preparations from first day post-infusion samples. These tended to level off and became intermediate between first and second day levels. It is postulated that the poor phagocytic competence of leukocytes from bovine mammary glands compared to their counterparts in blood observed by various workers may be due partially to low energy reserves in these cells.