Modulation of Na+ transport across leech skin by pesticides and heavy metals

Milde, Helga; Clauss, Wolfgang; Weber, Wolf-Michael

doi:10.1007/s00898-996-0008-x

Cited by 9 publications

(13 citation statements)

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“…The leech likely has a second class of DA receptors not positively coupled to cAMP. For example, DA but not cAMP inhibit ion transport across leech skin (Milde et al, 2001). Similarly, not all the effects of DA on the crawl circuit can be mimicked by PDIs, as evidenced by the improper phase relationships of DE-3 and CV and the inability of THP to reduce motoneuron excitability.…”

Section: Implication Of Multiple Da Receptor Subtypesmentioning

confidence: 99%

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Crisp

Gallagher

Mesce

2012

Journal of Experimental Biology

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SUMMARY Dopamine (DA) activates fictive crawling behavior in the medicinal leech. To identify the cellular mechanisms underlying this activation at the level of crawl-specific motoneuronal bursting, we targeted potential cAMP-dependent events that are often activated through DA 1 -like receptor signaling pathways. We found that isolated ganglia produced crawl-like motoneuron bursting after bath application of phosphodiesterase inhibitors (PDIs) that upregulated cAMP. This bursting persisted in salines in which calcium ions were replaced with equimolar cobalt or nickel, but was blocked by riluzole, an inhibitor of a persistent sodium current. PDI-induced bursting contained a number of patterned elements that were statistically similar to those observed during DA-induced fictive crawling, except that one motoneuron (CV) exhibited bursting during the contraction rather than the elongation phase of crawling. Although DA and the PDIs produced similar bursting profiles, intracellular recordings from motoneurons revealed differences in altered membrane properties. For example, DA lowered motoneuron excitability whereas the PDIs increased resting discharge rates. We suggest that PDIs (and DA) activate a sodium-influx-dependent timing mechanism capable of setting the crawl rhythm and that multiple DA receptor subtypes are involved in shaping and modulating the phase relationships and membrane properties of cell-specific members of the crawl network to generate crawling.

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Section: Implication Of Multiple Da Receptor Subtypesmentioning

confidence: 99%

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Crisp

Gallagher

Mesce

2012

Journal of Experimental Biology

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“…During the last years, the dorsal skin of the medical leech Hirudo medicinalis has been established as a valuable model system for the investigation of epithelial Na ϩ transport in invertebrates. In thorough electrophysiological studies using modified Ussing chambers, noise, and impedance analysis (15), the amiloride-sensitive Na ϩ transport across the dorsal skin of H. medicinalis was characterized in more detail (34,52,54). These studies revealed basic features of invertebrate Na ϩ absorption that showed some similarities with vertebrate ENaC: 40% of total Na ϩ uptake is amiloride-sensitive, but the affinity is somewhat lower [i.e., ϳ3 M vs. Յ 1 M for vertebrate ENaC (45)].…”

mentioning

confidence: 99%

Amiloride-sensitive sodium absorption is different in vertebrates and invertebrates

Sobczak

Willing

Kusche³

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Amiloride-sensitive Na+ absorption is a well-described feature of numerous transporting epithelia in vertebrates. Yet, very little is known about this important physiological process regarding invertebrates. In the present paper, we compare vertebrate Na+ absorption mediated by the amiloride-sensitive epithelial Na+ channel (ENaC) and its invertebrate counterpart. We used the dorsal skin of the annelid Hirudo medicinalis as a model for the Na+ absorption of invertebrate epithelia. In applying electrophysiological, molecular, and biochemical techniques we found striking functional and structural differences between vertebrate and invertebrate amiloride-sensitive Na+ absorption. Using modified Ussing chambers, we analyzed the influence of different known blockers and effectors of vertebrate ENaC on leech epithelial Na+ absorption. We demonstrate that the serine protease trypsin had no effect on the Na+ transport across leech integument, while it strongly activates vertebrate ENaC. While protons, and the divalent cations Ni2+ and Zn2+ stimulate vertebrate ENaC, amiloride-sensitive Na+ currents in leech integument were substantially reduced. For molecular studies, we constructed a cDNA library of Hirudo medicinalis and screened it with specific ENaC antibodies. We performed numerous PCR approaches using a vast number of different degenerated and specific ENaC primers to identify ENaC-like structures. Yet, both strategies did not reveal any ENaC-like sequence in leech integument. From these data we conclude that amiloride-sensitive Na+ absorption in leech skin is not mediated by an ENaC-like Na+ channel but by a still unknown invertebrate member of the ENaC/DEG family that we termed lENaTP (leech epithelial Na+ transporting protein).

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“…Such a system may be a useful defence mechanism in invertebrates. In annelids, particularly Hirudo medicinalis, it was shown that the integument, which faces the external conditions of the environment, has considerable resistance to environmental pollutants and heavy metals, and ion-transport mechanisms are not so heavily influenced by heavy metals as in vertebrates (Milde et al 1996b).…”

Section: Characterization Of Channels and Transporters At The Moleculmentioning

confidence: 99%

“…Leech dorsal skin mounted in an Ussing chamber has also been used as a suitable model for investigating the toxic effects of environmental pollutants (Milde et al 1996b). The action of pesticides and heavy metals on electrogenic sodium transport has been investigated.…”

Section: Absorption Of Ions and Watermentioning

confidence: 99%

Epithelial transport and osmoregulation in annelids

Clauss¹

2001

Can. J. Zool.

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Epithelial transport related to osmoregulation has so far not been extensively investigated in annelids. Compared with the large body of information about ion transport across crustacean or insect epithelia, only a few studies have been done with isolated preparations of annelids, using the body wall of marine polychaetes or Hirudinea. Nephridial function and general body homeostasis have received more attention, and have probably been best investigated in Hirudinea. With recent advances in the molecular physiology of epithelial transport systems in vertebrates, the cloning of various transporters and ion channels, and the considerable number of osmoregulatory peptides that have now been found and analyzed from annelids, it should now be possible, and is timely, to conduct functional studies on individual selected epithelial preparations or isolated cells from annelids. Such studies may be important for establishing useful models with somewhat less complexity than mammalian systems. For example, annelids lack aldosterone, an important osmoregulatory hormone, which is a key factor in the regulation of sodium reabsorption in vertebrates. Therefore, not only would such studies contribute to annelid physiology, but they would be important in a broader sense for understanding osmoregulation and its evolution. They should also facilitate the discovery and investigation of new specific regulatory pathways.

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Modulation of Na+ transport across leech skin by pesticides and heavy metals

Cited by 9 publications

References 0 publications

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Mechanisms contributing to the dopamine induction of crawl-like bursting in leech motoneurons

Amiloride-sensitive sodium absorption is different in vertebrates and invertebrates

Epithelial transport and osmoregulation in annelids

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