This study examined the acid-base and ionoregulatory responses by the skin and kidney of adult bullfrogs (Rana catesbiana) during
recovery from non-respiratory acidoses. Acidosis was induced by intravascular infusions of HCl (3,000 uequiv/kg), or NH4Cl (4,000 uequiv/kg), or by 45 min enforced submergence. Infused acids were immediately buffered by the extracellular fluids (ECF) and moved rapidly into the intracellular compartment. Clearance of the acid load was slow (> 24 h post-infusion) and only in NH4Cl loaded frogs was the full amount cleared within 5 days. Excess acid was excreted primarily by increased renal NH4+ effluxes. The skin contributed very little to the net acid excretion; instead large "base" losses ("acid" uptake) occurred. Acid infusions also resulted in large ion losses and elevated water uptake across the skin, with electrolytes and water moving down chemical gradients. Frogs infused with HCl died within 96 h; NH4Cl loaded frogs all survived.Forced submergence resulted in a severe lactacidosis which was corrected in 12 h by a combination of renal/cutaneous acid excretion (9:1 ratio) and metabolic utilization of lactate and H+ (~ 95% of excess acid load). Acid excretion occurred primarily as NH4+ efflux by the kidney and skin. A 1:1 exchange of Na+ influx/NH4+, efflux across the skin was found (r = 0.94; P < 0.01) when Jin Na+ was elevated over basal levels (30-40 uequiv/kg·h). Lactate and net acid effluxes by the skin and kidney diminished by 24 h post-disturbance and accounted for 4 to 6% of the total estimated load to the animal. All frogs survived the diving protocol. Restoration of acid-base state in acidotic bullfrogs by ECF and non-ECF mechanisms, as well as the renal and cutaneous responses to the acidosis, is discussed and compared to that of other vertebrates. It is concluded that anurans, and the bullfrog in particular, are poor regulators of acid-base state but instead are very tolerant to marked disturbances of acid-base balance. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24339 |
| Date | 12 1900 |
| Creators | Lindinger, Michael |
| Contributors | McDonald, D. G., Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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