Advanced

Spontaneous electrical and contractile activity correlated to 86Rb+ efflux in smooth muscle of guinea-pig mesotubarium

Hellstrand, Per LU and Lydrup, Marie-Louise (1988) In Journal of Physiology 407. p.587-597
Abstract
1. The spontaneous mechanical activity of guinea-pig mesotubarium consists of fused tetanic contractions lasting about 6 min, with a frequency of about four per hour. The muscle is completely relaxed between the contractions. Stretching the relaxed muscle elicits a contraction of the same appearance as the spontaneous ones. Comparison of preparations from oestrus (day 1 of the hormonal cycle), dioestrus (days 9-11) and prooestrus (days 14-15) showed no variation in the pattern of mechanical activity. 2. The resting membrane potential, measured by intracellular microelectrodes, did not differ with hormonal phase (prooestrus: -63.5 +/- 0.84 (n = 16); oestrus: -63.7 +/- 1.6 (n = 5); dioestrus: -61.6 +/- 0.77 (n = 17]. In most recordings a... (More)
1. The spontaneous mechanical activity of guinea-pig mesotubarium consists of fused tetanic contractions lasting about 6 min, with a frequency of about four per hour. The muscle is completely relaxed between the contractions. Stretching the relaxed muscle elicits a contraction of the same appearance as the spontaneous ones. Comparison of preparations from oestrus (day 1 of the hormonal cycle), dioestrus (days 9-11) and prooestrus (days 14-15) showed no variation in the pattern of mechanical activity. 2. The resting membrane potential, measured by intracellular microelectrodes, did not differ with hormonal phase (prooestrus: -63.5 +/- 0.84 (n = 16); oestrus: -63.7 +/- 1.6 (n = 5); dioestrus: -61.6 +/- 0.77 (n = 17]. In most recordings a depolarization of a few millivolts occurred during the relaxation period (5-10 min), but in a few cells a more pronounced spontaneous depolarization of 10-15 mV was found. Ouabain (1 microM) caused depolarization by about 9 mV, both in pro- and dioestrus, leading to the initiation of maintained repetitive spiking. 3. Contraction is preceded by a depolarization lasting 10-30 s, and when a threshold is reached a train of slow waves and spikes is elicited. The frequency of slow waves and the number of spikes on each slow wave progressively decrease during the contraction, until spiking eventually ceases. 4. The spikes are resistant to tetrodotoxin (0.5 microM) and disappear in Ca2+-free medium, which also causes membrane depolarization. The duration of contractions increased with Ca2+ concentration in the range 1-5 mM. 5. The rate of 86Rb+ efflux, expressed as fractional release in 2 min intervals, showed a consistent variation during the contractile cycle in preparations with regular spontaneous activity. Relative to the value at the end of the relaxed period the efflux rate increased by about twofold during the contraction. From the beginning of the relaxed period after the contraction the efflux rate decreased by about 25% until the beginning of the next contraction. 6. It is concluded that the contractile activity in the mesotubarium, as opposed to that of the fallopian tube (Lydrup & Hellstrand, 1986a), is independent of the hormonal phase, including the period around ovulation. The mechanism for initiation of the trains of action potentials associated with spontaneous contractions may involve a gradual decrease of permeability of K+ channels or activity of the Na+-K+ pump during the relaxed period. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physiology
volume
407
pages
587 - 597
publisher
The Physiological Society
external identifiers
  • pmid:3256626
  • scopus:0024238946
ISSN
1469-7793
language
English
LU publication?
yes
id
6a76b7ba-d0e6-49b3-9ffd-254c86d95901 (old id 1104236)
alternative location
http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1191221&blobtype=pdf
http://jp.physoc.org/cgi/reprint/407/1/587
date added to LUP
2008-08-07 13:04:16
date last changed
2017-08-20 04:33:03
@article{6a76b7ba-d0e6-49b3-9ffd-254c86d95901,
  abstract     = {1. The spontaneous mechanical activity of guinea-pig mesotubarium consists of fused tetanic contractions lasting about 6 min, with a frequency of about four per hour. The muscle is completely relaxed between the contractions. Stretching the relaxed muscle elicits a contraction of the same appearance as the spontaneous ones. Comparison of preparations from oestrus (day 1 of the hormonal cycle), dioestrus (days 9-11) and prooestrus (days 14-15) showed no variation in the pattern of mechanical activity. 2. The resting membrane potential, measured by intracellular microelectrodes, did not differ with hormonal phase (prooestrus: -63.5 +/- 0.84 (n = 16); oestrus: -63.7 +/- 1.6 (n = 5); dioestrus: -61.6 +/- 0.77 (n = 17]. In most recordings a depolarization of a few millivolts occurred during the relaxation period (5-10 min), but in a few cells a more pronounced spontaneous depolarization of 10-15 mV was found. Ouabain (1 microM) caused depolarization by about 9 mV, both in pro- and dioestrus, leading to the initiation of maintained repetitive spiking. 3. Contraction is preceded by a depolarization lasting 10-30 s, and when a threshold is reached a train of slow waves and spikes is elicited. The frequency of slow waves and the number of spikes on each slow wave progressively decrease during the contraction, until spiking eventually ceases. 4. The spikes are resistant to tetrodotoxin (0.5 microM) and disappear in Ca2+-free medium, which also causes membrane depolarization. The duration of contractions increased with Ca2+ concentration in the range 1-5 mM. 5. The rate of 86Rb+ efflux, expressed as fractional release in 2 min intervals, showed a consistent variation during the contractile cycle in preparations with regular spontaneous activity. Relative to the value at the end of the relaxed period the efflux rate increased by about twofold during the contraction. From the beginning of the relaxed period after the contraction the efflux rate decreased by about 25% until the beginning of the next contraction. 6. It is concluded that the contractile activity in the mesotubarium, as opposed to that of the fallopian tube (Lydrup & Hellstrand, 1986a), is independent of the hormonal phase, including the period around ovulation. The mechanism for initiation of the trains of action potentials associated with spontaneous contractions may involve a gradual decrease of permeability of K+ channels or activity of the Na+-K+ pump during the relaxed period.},
  author       = {Hellstrand, Per and Lydrup, Marie-Louise},
  issn         = {1469-7793},
  language     = {eng},
  pages        = {587--597},
  publisher    = {The Physiological Society},
  series       = {Journal of Physiology},
  title        = {Spontaneous electrical and contractile activity correlated to 86Rb+ efflux in smooth muscle of guinea-pig mesotubarium},
  volume       = {407},
  year         = {1988},
}