Temperature-induced changes in blood acid-base status in the alligator, Alligator mississipiensis

Abstract

Gas exchange and arterial blood acid-base status were measured in 13 conscious alligators, Alligator mississipiensis, at 15, 25, and 35 degrees C. Arterial pH decreased by 0.250 units (from 7.635 to 7.385) and arterial carbon dioxide partial pressure increased by 11.4 Torr (from 11.8 to 23.2) as body temperature increased from 15 to 35 degrees C. No statistically significant changes occurred in arterial bicarbonate concentration. When OH-/H+ and alpha-imidazole were compared at each temperature, more variability was observed in OH-/H+, which increased from 8.7 to 12.0 as temperature increased from 15 to 35 degrees C. alpha-Imidazole remained essentially constant (0.76 at 15 degrees C and 0.80 at 35 degrees C). Body temperature increase caused marked increases in minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2). The relative changes in these parameters resulted in a decrease in both VE/VO2 and VE/VCO2. The data of the present study are consistent with the concept that poikilotherms regulate their alveolar ventilation with changes in body temperature in order to keep OH-/H+ or alpha-imidazole constant.

Surgical removal of right-to-left cardiac shunt in the American alligator(Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving

“…Our values for resting respiratory frequency, tidal volume and minute ventilation at 23°C are within the range previously reported for alligators at 25°C (Davies, 1978;Hicks and White, 1992), and our ranges of voluntary apnoea length (grand mean and maximum apnoea time) are comparable to previously reported data on wild and captive crocodilians (Grigg et al, 1985;Wright, 1987;Wright et al, 1992;Seebacher et al, 2005;Uriona et al, 2009) [see Table2 in Uriona et al (Uriona et al, 2009) for summary of previous data]. Davies (Davies, 1978) reported a V O2 (~1.0mlkg…”

“…Wet air was sub-sampled downstream of the pneumotach and pulled through an oxygen analyser (S-3A Applied Electrochemistry) at 140mlmin -1 (Davies, 1978;Hicks and White, 1992). Flow rates were determined and maintained using calibrated rotameters (Cole-Parmer, Vernon Hills, IL, USA), and signals were collected at 20Hz using AcqKnowledge data acquisition software and an A/D MP100 board.…”

Shunting and survival in alligators

“…The effect of temperature on acid-base status has been studied in many ectotherms, with the first work on alligators by Austin et al (1927). The general trend observed is that with an increase in temperature, pH decreases and PCO2 increases (Jackson and Kagen, 1976;Reeves, 1977;Davies, 1978;Davies etal, 1982;Heisler, 1986;Weber and White, 1986). It is thought that ectothermic air-breathers adjust blood PCO2 in response to temperature changes via adjustments in ventilation, particularly the air convection requirement (ACR; relative ventilation; VE/VO2; VE/VCO2).…”

“…Alligators have a preferred body temperature of 31° C and digestion and absorption of nutrients are slow and incomplete at temperatures lower than 25° C (Coulson and Coulson, 1986;Coulson et al, 1990). Alligators were exposed for 16 weeks to 20° C, although most studies have only looked at acid-base changes in response to temperature changes for hours or days (Austin et al, 1927;Davies, 1978;Davies et al, 1982;Lutz etal, 1989;Douse and Mitchell, 1991). Our alligators were kept at 20° C for many weeks to ensure that no additional time dependent changes in acid-base status would occur as a result of metabolic changes or strong ion adjustments.…”

Methemoglobin reduction in crocodile blood: Are high levels of MetHb typical of healthy reptiles?

“…With an increase in body temperature in reptiles arterial pH decreases and arterial PCO 2 increases, but total CO? remains constant (Davies, 1978). These changes are accomplished by decreasing; the rates between pulmonary ventilation and metabolic rate in order to maintain a -y5constant relative blood alkalinity (OH /H + ) or fractional dissociation of cx-imidazole groups of blood proteins (Davies, 1978).…”