TY - JOUR
T1 - First evidence of epithelial transport in tardigrades
T2 - a comparative investigation of organic anion transport
AU - Halberg, Kenneth Agerlin
AU - Møbjerg, Nadja
PY - 2012/2
Y1 - 2012/2
N2 - We investigated transport of the organic anion Chlorophenol Red (CPR) in the tardigrade Halobiotus crispae using a new method for quantifying non-fluorescent dyes. We compared the results acquired from the tardigrade with CPR transport data obtained from Malpighian tubules of the desert locust Schistocerca gregaria. CPR accumulated in the midgut lumen of H. crispae, indicating that organic anion transport takes place here. Our results show that CPR transport is inhibited by the mitochondrial un-coupler DNP (1 mmoll -1; 81% reduction), the Na +/K +-ATPase inhibitor ouabain (10 mmoll -1; 21% reduction) and the vacuolar H +-ATPase inhibitor bafilomycin (5μmoll -1; 21% reduction), and by the organic anions PAH (10 mmoll -1; 44% reduction) and probenecid (10 mmoll -1; 61% reduction, concentration-dependent inhibition). Transport by locust Malpighian tubules exhibits a similar pharmacological profile, albeit with markedly higher concentrations of CPR being reached in S. gregaria. Immunolocalization of the Na +/K +-ATPase -subunit in S. gregaria revealed that this transporter is abundantly expressed and localized to the basal cell membranes. Immunolocalization data could not be obtained from H. crispae. Our results indicate that organic anion secretion by the tardigrade midgut is transporter mediated with likely candidates for the basolateral entry step being members of the Oat and/or Oatp transporter families. From our results, we cautiously suggest that apical H + and possibly basal Na +/K + pumps provide the driving force for the transport; the exact coupling between electrochemical gradients generated by the pumps and transport of ions, as well as the nature of the apical exit step, are unknown. This study is, to our knowledge, the first to show active epithelial transport in tardigrades.
AB - We investigated transport of the organic anion Chlorophenol Red (CPR) in the tardigrade Halobiotus crispae using a new method for quantifying non-fluorescent dyes. We compared the results acquired from the tardigrade with CPR transport data obtained from Malpighian tubules of the desert locust Schistocerca gregaria. CPR accumulated in the midgut lumen of H. crispae, indicating that organic anion transport takes place here. Our results show that CPR transport is inhibited by the mitochondrial un-coupler DNP (1 mmoll -1; 81% reduction), the Na +/K +-ATPase inhibitor ouabain (10 mmoll -1; 21% reduction) and the vacuolar H +-ATPase inhibitor bafilomycin (5μmoll -1; 21% reduction), and by the organic anions PAH (10 mmoll -1; 44% reduction) and probenecid (10 mmoll -1; 61% reduction, concentration-dependent inhibition). Transport by locust Malpighian tubules exhibits a similar pharmacological profile, albeit with markedly higher concentrations of CPR being reached in S. gregaria. Immunolocalization of the Na +/K +-ATPase -subunit in S. gregaria revealed that this transporter is abundantly expressed and localized to the basal cell membranes. Immunolocalization data could not be obtained from H. crispae. Our results indicate that organic anion secretion by the tardigrade midgut is transporter mediated with likely candidates for the basolateral entry step being members of the Oat and/or Oatp transporter families. From our results, we cautiously suggest that apical H + and possibly basal Na +/K + pumps provide the driving force for the transport; the exact coupling between electrochemical gradients generated by the pumps and transport of ions, as well as the nature of the apical exit step, are unknown. This study is, to our knowledge, the first to show active epithelial transport in tardigrades.
U2 - 10.1242/jeb.065987
DO - 10.1242/jeb.065987
M3 - Journal article
C2 - 22246258
SN - 0022-0949
VL - 215
SP - 497
EP - 507
JO - Journal of Experimental Biology
JF - Journal of Experimental Biology
IS - 3
ER -