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Meleagris gallopavo with its average incubation period of 28 days (D) is in the middle of incubation periods of the chicken Gallus gallus f. domesticus (21D) and the muscovy duck Cairina moshata (35D). This study is about influence of incubation temperature (Ta) on activity of embryonic ß1-adrenoceptor (ß1-AC) on D23 and D25. D23 and D25 were choosen, because of relation to studies on chicken embryos, which were done by Lewin (1). D23/D25 are not exactly equivalent to D18 and D20 in chicken embryonic development, but we wanted to examine embryos without internal pipping, which appears on D26 in turkey embryos. We used heart rate (HR) as parameter for ß1-AC activity. We found, Ta has less influence on ß1-AC activity in elder turkey embryos than in younger ones. Lowering Ta down to 35,5°C has not such differences in its effects on HR between D23 and D25 than there are when Ta was rised up to 38,5°C. This fact is repeated in the results of our studies with intracellular cAMP. The cAMP content of embryonic heartmuscle cells on D25 is lower than on D23 in all three Ta-groups (35,5°C; 37,5°C; 38,5°C). And at 35,5°C there is a higher cAMP content left on D25 compared with the other two Ta´s on D25. So the decrease at lower Ta is not as big as it is at higher Ta. These facts are hints, that heartmuscle cells of precocial avian embryos are able to maintain cellular mechanism at lower Ta even better than they do at higher Ta.
1. Lewin R, Dörner M, and Tönhardt H. Pulse Oxymetry- a new way of determing the heart rate in chicken embryos. Pflugers Arch.434 (5), 639-641,1997.
This study is supported by the H. W. Schaumann Foundation