Schwieterman Gail D, Rummer Jodie L, Bouyoucos Ian A, Bushnell Peter G, Brill Richard W
Department of Fisheries Science, Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA 23062, United States of America.
Australian Research Council Centre of Excellence for Coral Reef Studies, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Aug;258:110978. doi: 10.1016/j.cbpa.2021.110978. Epub 2021 May 11.
In teleost fishes, catecholamine-induced increases in the activity of cation exchangers compensate for decreases in hemoglobin oxygen affinity and maximum blood oxygen carrying capacity caused by decreases in plasma pH (i.e., metabolic acidosis). The resultant red blood cell (RBC) swelling has been documented in sandbar (Carcharhinus plumbeus) and epaulette (Hemiscyllium ocellatum) sharks following capture by rod-and-reel or after a 1.5 h exposure to anoxia (respectively), although the underlying mechanisms remain unknown. To determine if RBC swelling could be documented in other elasmobranch fishes, we collected blood samples from clearnose skate (Rostroraja eglanteria), blacktip reef shark (Carcharhinus melanopterus), and sicklefin lemon shark (Negaprion acutidens) subjected to exhaustive exercise or air exposure (or both) and measured hematocrit, hemoglobin concentration, RBC count, RBC volume, and mean corpuscular hemoglobin content. We did likewise with sandbar and epaulette sharks to further explore the mechanisms driving swelling when present. We could not document RBC swelling in any species; although hematocrit increased in all species (presumably due to RBC ejection from the spleen or fluid shifts out of the vascular compartment) except epaulette shark. Our results indicate RBC swelling and associated ion shifts in elasmobranch fishes is not inducible by exercise or hypoxia, thus implying this response maybe of lesser importance for maintaining oxygen delivery during acute acidosis than in teleost fishes.
在硬骨鱼类中，儿茶酚胺引起的阳离子交换器活性增加可补偿因血浆pH值降低（即代谢性酸中毒）导致的血红蛋白氧亲和力和最大血液携氧能力的下降。在沙洲鲨（铅灰真鲨）和肩章鲨（斑点半锯鲨）被钓竿钓获后或分别暴露于缺氧环境1.5小时后，已观察到红细胞肿胀现象，尽管其潜在机制尚不清楚。为了确定其他软骨鱼类是否也会出现红细胞肿胀，我们采集了经过力竭运动或暴露于空气中（或两者皆有）的白吻犁头鳐、黑鳍礁鲨和镰状柠檬鲨的血样，测量了血细胞比容、血红蛋白浓度、红细胞计数、红细胞体积和平均红细胞血红蛋白含量。我们对沙洲鲨和肩章鲨也进行了同样的操作，以进一步探究出现肿胀时的驱动机制。我们在任何物种中都未观察到红细胞肿胀；尽管除肩章鲨外，所有物种的血细胞比容均有所增加（可能是由于红细胞从脾脏排出或液体从血管腔转移）。我们的结果表明，软骨鱼类中的红细胞肿胀及相关离子转移不会因运动或缺氧而诱导产生，因此这意味着这种反应在急性酸中毒期间对于维持氧气输送的重要性可能低于硬骨鱼类。
