The mechanism of blood flow redistribution within the carotid labyrinth of the toad,Bufo marinus
✍ Scribed by Smith, D. G. ;Rogers, D. C. ;Chamley-Campbell, J. ;Campbell, G. R.
- Publisher
- John Wiley and Sons
- Year
- 1981
- Tongue
- English
- Weight
- 752 KB
- Volume
- 216
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
The mechanism of flow redistribution in the carotid labyrinth of the toad, Bufo marinus, was investigated by exposing saline‐perfused labyrinths and cultured explants of cells from the pars capillaris or p. cavernosa to various vasoactive compounds. In addition, the presence of smooth muscle myosin and tropomyosin was demonstrated by immunofluorescence histochemistry. Explants from the p. capillaris were found to be unresponsive to all agonists tested, whereas those from the p. cavernosa were contracted by each of angiotensin, adrenaline, and acetylcholine. The same agonists always reduced the proportion of total perfusion leaving the labyrinth via the external carotid artery while simultaneously raising the overall resistance to flow through the organ. It is concluded that flow through the external carotid artery is controlled by smooth muscle cells encircling it at its base or by others surrounding the radicles to the ring vessel: Flow through the p. capillaris to the internal carotid is not controlled by β‐cells or their processes. Internal carotid flow may be controlled actively by constriction of the internal carotid itself, or passively as a consequence of altered pressure gradients within the labyrinth during constriction of the external carotid artery.