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Cardiovascular control mechanisms in the antarctic fish pagothenia borchgrevinki
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Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) S1~9108
D E X A M E T H A S O N E AND A I ) R E N A L I N E S T I M U L A T E P U L M O N A R Y S U R F A C T A N T S E C R E T I O N IN E M B R Y O N I C C H I C K E N L U N G S Lucy C. Sullivan and Sandra Orgeig Department o f Environmental Biology, University o f Adelaide, Adelaide, SA, 5005, Australia Pulmonary surfactant (PS), a mixture ofphospholipids and proteins secreted by alveolar type 1I cells, functions to reduce the surface tension in the lungs o f all air-breathing vertebrates. While the surfactant system is highly conserved amongst the vertebrates, differences in birthing strategy could lead to differences in the mechanisms and timing of control o f development o f the pulmonary surfactant system. Here, we examine the control o f secretion o f PS during lung development in a homeothermic egg-laying vertebrate. In mammals, glucocorticoids and autonomic neurotransmitters contribute to the maturation o f the surfactant system. Therefore, we examined the effects of dexamethasone, epinephrine and carbachol on PS secretion from cultured type !1 cells o f the developing chicken lung. As dexamethasone is believed to act on type 1I cells through paracrine factors released from interstitial fibroblasts, type II cells and lung fibroblasts were isolated and cocultured from chickens following 16, 18 and 20 days of incubation and from hatchlings (day 21). Epinephrine stimulated phosphatidylcholine (PC) secretion at all stages, whereas dexamethasone stimulated secretion of PC at days 16 and 18. Carbachol had no effect at any stage. Therefore, similar control mechanisms are present in the chicken and eutherian mammals, despite the vastly different birthing strategies and lung structure and function. This provides additional evidence for the highly conserved nature o f the entire surfactant system.
CARDIOVASCULAR CONTROL PAGOTHENIA BORCHGREVINKI
MECHANISMS
IN
THE
ANTARCTIC
FISH
Lena Sundin Dept. ofZoology/Zoophysiology, G6teborg University, Sweden Serotonin and adenosine are putative cardiovascular regulators during environmental hypoxia in fish. As fish in Antarctica live in cold and well oxygenated waters, and have been genetically isolated for 15-25 million years, we took the opportunity to explore the cardiovascular effects of these agents on the red-blooded Antarctic notothenioid fish Pagothenia borchgrevinki (Boulenger). The fish were caught by line and honk in McMurdo Sound, Antarctica and transported back to Scott Base where they were kept in plastic tanks at -1.3 to -0.8 °C. Serotonin (O.lnmol/kg) and adenosine (lOnmol/kg) injected into the ven~'al aorta increased the brandfial resistance and decreased the arterial PO2. The fall in PO2 was larger in animals with a higher pro-injection arterial PO2 and it suggests that the level of the branchial resistance directly reflect the effectiveness of oxygen uptake. The branchial constriction induced by serotonin and adenosine was mimicked by specific receptor agonists and blocked by specific antagonists, showing that the involved receptors are 5-HT2 and A1 respectively. For comparison, the rainbow trout also have excitatory serotonergic and adenosinergie Ixandlial mechanisms, but the gill vessels of Borchs are about 1000 times more sensitive to serotonin. Heart rate was markedly reduced by adenosincrgic mechanisms and both agmists inctcased stroke volume and decreased the systemic resistance. While the serotonin-induced effects neither could be mimicked nor abolished by selective receptor tools, the adenosine-induced responses could, and thus these may also be elicited by Am-receptor activated mechanisms. This work shows that serotonergic and adenosinergic cardiovascular control mechanisms are present in Antarctic notothenioids, and as such these mechanisms must have another pivotal role to play than to adjust the cardiovascular system during environmental hypoxia.
Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) S1~9108
D E X A M E T H A S O N E AND A I ) R E N A L I N E S T I M U L A T E P U L M O N A R Y S U R F A C T A N T S E C R E T I O N IN E M B R Y O N I C C H I C K E N L U N G S Lucy C. Sullivan and Sandra Orgeig Department o f Environmental Biology, University o f Adelaide, Adelaide, SA, 5005, Australia Pulmonary surfactant (PS), a mixture ofphospholipids and proteins secreted by alveolar type 1I cells, functions to reduce the surface tension in the lungs o f all air-breathing vertebrates. While the surfactant system is highly conserved amongst the vertebrates, differences in birthing strategy could lead to differences in the mechanisms and timing of control o f development o f the pulmonary surfactant system. Here, we examine the control o f secretion o f PS during lung development in a homeothermic egg-laying vertebrate. In mammals, glucocorticoids and autonomic neurotransmitters contribute to the maturation o f the surfactant system. Therefore, we examined the effects of dexamethasone, epinephrine and carbachol on PS secretion from cultured type !1 cells o f the developing chicken lung. As dexamethasone is believed to act on type 1I cells through paracrine factors released from interstitial fibroblasts, type II cells and lung fibroblasts were isolated and cocultured from chickens following 16, 18 and 20 days of incubation and from hatchlings (day 21). Epinephrine stimulated phosphatidylcholine (PC) secretion at all stages, whereas dexamethasone stimulated secretion of PC at days 16 and 18. Carbachol had no effect at any stage. Therefore, similar control mechanisms are present in the chicken and eutherian mammals, despite the vastly different birthing strategies and lung structure and function. This provides additional evidence for the highly conserved nature o f the entire surfactant system.
CARDIOVASCULAR CONTROL PAGOTHENIA BORCHGREVINKI
MECHANISMS
IN
THE
ANTARCTIC
FISH
Lena Sundin Dept. ofZoology/Zoophysiology, G6teborg University, Sweden Serotonin and adenosine are putative cardiovascular regulators during environmental hypoxia in fish. As fish in Antarctica live in cold and well oxygenated waters, and have been genetically isolated for 15-25 million years, we took the opportunity to explore the cardiovascular effects of these agents on the red-blooded Antarctic notothenioid fish Pagothenia borchgrevinki (Boulenger). The fish were caught by line and honk in McMurdo Sound, Antarctica and transported back to Scott Base where they were kept in plastic tanks at -1.3 to -0.8 °C. Serotonin (O.lnmol/kg) and adenosine (lOnmol/kg) injected into the ven~'al aorta increased the brandfial resistance and decreased the arterial PO2. The fall in PO2 was larger in animals with a higher pro-injection arterial PO2 and it suggests that the level of the branchial resistance directly reflect the effectiveness of oxygen uptake. The branchial constriction induced by serotonin and adenosine was mimicked by specific receptor agonists and blocked by specific antagonists, showing that the involved receptors are 5-HT2 and A1 respectively. For comparison, the rainbow trout also have excitatory serotonergic and adenosinergie Ixandlial mechanisms, but the gill vessels of Borchs are about 1000 times more sensitive to serotonin. Heart rate was markedly reduced by adenosincrgic mechanisms and both agmists inctcased stroke volume and decreased the systemic resistance. While the serotonin-induced effects neither could be mimicked nor abolished by selective receptor tools, the adenosine-induced responses could, and thus these may also be elicited by Am-receptor activated mechanisms. This work shows that serotonergic and adenosinergic cardiovascular control mechanisms are present in Antarctic notothenioids, and as such these mechanisms must have another pivotal role to play than to adjust the cardiovascular system during environmental hypoxia.