Hypoxanthine-guanine phosphoribosyltransferase and inosine 5′-monophosphate dehydrogenase activities in three mammalian species: aquatic (Mirounga angustirostris), semi-aquatic (Lontra longicaudis annectens) and terrestrial (Sus scrofa)

Myrna Barjau Pérez-Milicua,Daniel E Crocker,Juan P Gallo-Reynoso,Tania Zenteno-Savín

doi:10.3389/fphys.2015.00212

Abstract

Aquatic and semiaquatic mammals have the capacity of breath hold (apnea) diving. Northern elephant seals (Mirounga angustirostris) have the ability to perform deep and long duration dives; during a routine dive, adults can hold their breath for 25 min. Neotropical river otters (Lontra longicaudis annectens) can hold their breath for about 30 s. Such periods of apnea may result in reduced oxygen concentration (hypoxia) and reduced blood supply (ischemia) to tissues. Production of adenosine 5′-triphosphate (ATP) requires oxygen, and most mammalian species, like the domestic pig (Sus scrofa), are not adapted to tolerate hypoxia and ischemia, conditions that result in ATP degradation. The objective of this study was to explore the differences in purine synthesis and recycling in erythrocytes and plasma of three mammalian species adapted to different environments: aquatic (northern elephant seal) (n = 11), semiaquatic (neotropical river otter) (n = 4), and terrestrial (domestic pig) (n = 11). Enzymatic activity of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) was determined by spectrophotometry, and activity of inosine 5′-monophosphate dehydrogenase (IMPDH) and the concentration of hypoxanthine (HX), inosine 5′-monophosphate (IMP), adenosine 5′-monophosphate (AMP), adenosine 5′-diphosphate (ADP), ATP, guanosine 5′-diphosphate (GDP), guanosine 5′-triphosphate (GTP), and xanthosine 5′-monophosphate (XMP) were determined by high-performance liquid chromatography (HPLC). The activities of HGPRT and IMPDH and the concentration of HX, IMP, AMP, ADP, ATP, GTP, and XMP in erythrocytes of domestic pigs were higher than in erythrocytes of northern elephant seals and river otters. These results suggest that under basal conditions (no diving, sleep apnea or exercise), aquatic, and semiaquatic mammals have less purine mobilization than their terrestrial counterparts.

Highlights

Purine nucleotides and their related metabolic products are involved in many biological processes (Carver, 1999; Pang et al, 2012)
Enzyme Activity hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and inosine 5′-monophosphate dehydrogenase (IMPDH) activities in samples from domestic pigs, river otters, and northern elephant seals are summarized in Figures 1, 2
IMPDH activity in plasma samples from domestic pigs, river otters, and northern elephant seals was below detection limit

Summary

Introduction

Purine nucleotides and their related metabolic products are involved in many biological processes (Carver, 1999; Pang et al, 2012). Most mammalian species have low or no tolerance to lack of oxygen, and cells and tissues become compromised during prolonged episodes of decreased tissue oxygen content (hypoxia) (Boutilier and St-Pierre, 2000) Aquatic mammals such as elephant seals and sperm whales can tolerate prolonged periods of hypoxia, related to dive-associated breath hold (apneas) (Elsner, 1999). Northern elephant seals (Mirounga angustirostris) dive continuously while at sea, to mean depths over 500 m and mean durations over 23 min, followed by short surface intervals of 2–3 min (Robinson et al, 2012) These dives are associated with unusual degrees of systemic hypoxia (Meir et al, 2009). Terrestrial mammals, such as humans and domestic pigs, are not adapted to diving, the diving response (bradycardia, peripheral vasoconstriction, blood flow redistribution) is similar to that observed in aquatic and semiaquatic mammals; the extent of the response (reduction of heart rate, for instance) is greater in diving mammals (Panneton, 2013)

Objectives

Methods

Results

Conclusion