Cold acclimation increases cold tolerance of chill-susceptible insects and the acclimation response often involves improved organismal ion balance and osmoregulatory function at low temperature. However, the physiological mechanisms underlying plasticity of ion regulatory capacity are largely unresolved. Here we used Ussing chambers to explore the effects of cold exposure on hindgut KCl reabsorption in cold- (11 °C) and warm-acclimated (30 °C) Locusta migratoria. Cooling (from 30 to 10 °C) reduced active reabsorption across recta from warm-acclimated locusts, while recta from cold-acclimated locusts maintained reabsorption at 10 °C. The differences in transport capacity were not linked to major rearrangements of membrane phospholipid profiles. Yet, the stimulatory effect of two signal transduction pathways were altered by temperature and/or acclimation. cAMP-stimulation increased reabsorption in both acclimation groups, with a strong stimulatory effect at 30 °C and a moderate stimulatory effect at 10 °C. cGMP-stimulation also increased reabsorption in both acclimation groups at 30 °C, but their response to cGMP differed at 10 °C. Recta from warm-acclimated locusts, characterised by reduced reabsorption at 10 °C, recovered reabsorption capacity following cGMP-stimulation at 10 °C. In contrast, recta from cold-acclimated locusts, characterised by sustained reabsorption at 10 °C, were unaffected by cGMP-stimulation. Furthermore, cold-exposed recta from warm-acclimated locusts were insensitive to bafilomycin-α1, a V-type H+-ATPase inhibitor, whereas this blocker reduced reabsorption across cold-exposed recta from cold-acclimated animals. In conclusion, bafilomycin-sensitive and cGMP-dependent transport mechanism(s) are likely blocked during cold exposure in warm-acclimated animals while preserved in cold-acclimated animals. These may in part explain the large differences in rectal ion transport capacity between acclimation groups at low temperature.

• Klíčová slova
• Cold tolerance, Membrane phospholipid, Temperature, Ussing chamber, V-type H(+)-ATPase, cGMP/cAMP signaling pathways,
• MeSH
• aklimatizace fyziologie   MeSH
• AMP cyklický metabolismus   MeSH
• guanosinmonofosfát cyklický metabolismus   MeSH
• iontový transport MeSH
• Locusta migratoria fyziologie   MeSH
• metabolismus lipidů MeSH
• nízká teplota * MeSH
• trávicí systém metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AMP cyklický MeSH
• guanosinmonofosfát cyklický MeSH

Cold exposure depolarizes cells in insects due to a reduced electrogenic ion transport and a gradual increase in extracellular K+ concentration ([K+]). Cold-induced depolarization is linked to cold injury in chill-susceptible insects, and the locust, Locusta migratoria, has been shown to improve cold tolerance following cold acclimation through depolarization resistance. Here we investigate how cold acclimation influences depolarization resistance and how this resistance relates to improved cold tolerance. To address this question, we investigated if cold acclimation affects the electrogenic transport capacity and/or the relative K+ permeability during cold exposure by measuring membrane potentials of warm- and cold-acclimated locusts in the presence and absence of ouabain (Na+-K+ pump blocker) or 4-aminopyridine (4-AP; voltage-gated K+ channel blocker). In addition, we compared the membrane lipid composition of muscle tissue from warm- and cold-acclimated locust and the abundance of a range transcripts related to ion transport and cell injury accumulation. We found that cold-acclimated locusts are depolarization resistant due to an elevated K+ permeability, facilitated by opening of 4-AP-sensitive K+ channels. In accordance, cold acclimation was associated with an increased abundance of Shaker transcripts (gene encoding 4-AP-sensitive voltage-gated K+ channels). Furthermore, we found that cold acclimation improved muscle cell viability following exposure to cold and hyperkalemia even when muscles were depolarized substantially. Thus cold acclimation confers resistance to depolarization by altering the relative ion permeability, but cold-acclimated locusts are also more tolerant to depolarization.

• Klíčová slova
• acclimation, cold exposure, depolarization, insect,
• MeSH
• 4-aminopyridin farmakologie   MeSH
• aklimatizace účinky léků   fyziologie   MeSH
• kosterní svalová vlákna účinky léků   fyziologie   MeSH
• Locusta migratoria fyziologie   MeSH
• membránové potenciály účinky léků   fyziologie   MeSH
• nízká teplota * MeSH
• ouabain farmakologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 4-aminopyridin MeSH
• ouabain MeSH

The diacylglycerols (DG) molecular species and their fatty acid (FA) composition were investigated by electrospray mass spectrometry (ESI-MS) and by gas chromatography with flame ionisation detection (GC-FID) in haemolymph of Locusta migratoria after application of adipokinetic hormones Locmi-AKH-I, -II and -III. The analyses showed (1) a heterogeneous distribution of individual DGs in haemolymph after the hormone application. The results revealed that mobilization of the DGs is molecular species-specific with the highest proportion of 34:1 DG (16:0/18:1 - mw 594Da) for all Locmi-AKHs bearing palmitic acid (C16:0) and oleic acid (C18:1) residues, and forming about 20% of the total mobilized DG content. (2) Analysis of fat body triacylglycerols revealed that all Locmi-AKHs mobilize the DGs selectively with the preference of those possessing the C18 and C16 FAs. The fat body FAs with carbon chain longer than 18 did not participate in the mobilization. (3) A distribution of FAs in the DG structures obtained by LC/ESI-MS, and FA analysis by GC-FID after transmethylation indicated a certain degree of Locmi-AKH selectivity toward the mobilized DGs and hence the FAs. The Locmi-AKH-I significantly prefers mobilization of DGs containing unsaturated FAs, while Locmi-AKH-II and -III prefer mobilization of saturated FAs.

• MeSH
• diglyceridy metabolismus   MeSH
• hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
• hmyzí hormony metabolismus   MeSH
• hmyzí proteiny metabolismus   MeSH
• kyselina pyrrolidonkarboxylová analogy a deriváty   metabolismus   MeSH
• Locusta migratoria metabolismus   MeSH
• oligopeptidy metabolismus   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adipokinetic hormone MeSH Prohlížeč
• diglyceridy MeSH
• hmyzí hormony MeSH
• hmyzí proteiny MeSH
• kyselina pyrrolidonkarboxylová MeSH
• oligopeptidy MeSH