A large number of blood samples was taken from the jugular vein of 18 cows or heifers during parturition, especially during stage II. In 9 animals an increase in serum growth hormone was observed and the peak occurred within the period which began when the forelegs of the calf became visible in the vulva, and ended a few minutes after expulsion of the calf. In typical cases, the growth hormone peak was preceded by a progressive increase, and followed by a gradual decrease in the hormone level. The total duration of the phenomenon amounted to a few hours. During the days before and after parturition, no change in growth hormone concentration could be noted. The serum free fatty acid values were high during parturition.

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PubMedDate not supplied

Comparison of bovine platelet and teat alpha 2-adrenoceptor characteristics by [3H]rauwolscine binding.

Alpha 2-adrenoceptors on platelet membranes, isolated from "slaughterhouse cows," were characterized by [3H]-rauwolscine binding. There were 30 +/- 3 [3H]rauwolscine sites per platelet, corresponding to 194 +/- 18 fmol/mg protein. These had an equilibrium dissociation constant (KD) of 5.25 +/- 0.56 nM, a Hill coefficient of 1.00 +/- 0.01 (n = 9), and were competed for by adrenergic compounds stereoselectively. The rank order of catecholamines coincided with that expected for alpha 2-adrenoceptors. Ki-values for inhibition of specific [3H]rauwolscine binding by 7 agonists and 6 antagonists were in the same range as previously observed in teat tissue. It is therefore concluded that quite similar [3H]rauwolscine binding sites were identified and characterized in both bovine teats and platelets. Direct comparison of binding characteristics between alpha 2-adrenoceptors from teat tissue and platelets of the same "primiparous cows," revealed no difference in binding affinity, although a significant higher platelet receptor number was noted in the platelets (platelets: 353 fmol/mg protein; teat tissue: 91 fmol/mg protein; n = 10).

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PubMedDate not supplied

Influence of suckling on the bovine growth hormone levels in the blood of lactating cow.

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