Furaptra (Raju, B., E. Murphy, L. A. Levy, R. D. Hall, and R. E. London. 1989. Am. J. Physiol. 256:C540-C548) is a "tri-carboxylate" fluorescent indicator with a chromophore group similar to that of fura-2 (Grynkiewicz, G., M. Poenie, and R. Y. Tsien. 1985. J. Biol. Chem. 260:3440-3450). In vitro calibrations indicate that furaptra reacts with Ca2+ and Mg2+ with 1:1 stoichiometry, with dissociation constants of 44 microM and 5.3 mM, respectively (16-17 degrees C; ionic strength, 0.15 M; pH, 7.0). Thus, in a frog skeletal muscle fiber stimulated electrically, the indicator is expected to respond to the change in myoplasmic free [Ca2+] (delta[Ca2+]) with little interference from changes in myoplasmic free [Mg2+]. The apparent longitudinal diffusion constant of furaptra in myoplasm was found to be 0.68 (+/- 0.02, SEM) x 10(-6) cm2 s-1 (16-16.5 degrees C), a value which suggests that about half of the indicator was bound to myoplasmic constituents of large molecular weight. Muscle membranes (surface and/or transverse-tubular) appear to have some permeability to furaptra, as the total quantity of indicator contained within a fiber decreased after injection; the average time constant of the loss was 302 (+/- 145, SEM) min. In fibers containing less than 0.5 mM furaptra and stimulated by a single action potential, the calibrated peak value of delta[Ca2+] averaged 5.1 (+/- 0.3, SEM) microM. This value is about half that reported in the preceding paper (9.4 microM; Konishi, M., and S. M. Baylor. 1991. J. Gen. Physiol. 97:245-270) for fibers injected with purpurate-diacetic acid (PDAA). The latter difference may be explained, at least in part, by the likelihood that the effective dissociation constant of furaptra for Ca2+ is larger in vivo than in vitro, owing to the binding of the indicator to myoplasmic constituents. The time course of furaptra's delta[Ca2+], with average values (+/- SEM) for time to peak and half-width of 6.3 (+/- 0.1) and 9.5 (+/- 0.4) ms, respectively, is very similar to that of delta[Ca2+] recorded with PDAA. Since furaptra's delta[Ca2+] can be recorded at a single excitation wavelength (e.g., 420 nm) with little interference from fiber intrinsic changes, movement artifacts, or delta[Mg2+], furaptra represents a useful myoplasmic Ca2+ indicator, with properties complementary to those of other available indicators.
Skip Nav Destination
Article navigation
1 February 1991
Article|
February 01 1991
Myoplasmic calcium transients in intact frog skeletal muscle fibers monitored with the fluorescent indicator furaptra.
M Konishi,
M Konishi
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
Search for other works by this author on:
S Hollingworth,
S Hollingworth
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
Search for other works by this author on:
A B Harkins,
A B Harkins
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
Search for other works by this author on:
S M Baylor
S M Baylor
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
Search for other works by this author on:
M Konishi
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
S Hollingworth
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
A B Harkins
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
S M Baylor
Department of Physiology, University of Pennsylvania Medical Center, Philadelphia 19104-6085.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1991) 97 (2): 271–301.
Citation
M Konishi, S Hollingworth, A B Harkins, S M Baylor; Myoplasmic calcium transients in intact frog skeletal muscle fibers monitored with the fluorescent indicator furaptra.. J Gen Physiol 1 February 1991; 97 (2): 271–301. doi: https://doi.org/10.1085/jgp.97.2.271
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSuggested Content
Myoplasmic calcium transients monitored with purpurate indicator dyes injected into intact frog skeletal muscle fibers.
J Gen Physiol (February,1991)
The amplitude and time course of the myoplasmic free [Ca2+] transient in fast-twitch fibers of mouse muscle.
J Gen Physiol (November,1996)
Effect of fura-2 on action potential-stimulated calcium release in cut twitch fibers from frog muscle.
J Gen Physiol (August,1993)
Email alerts
Advertisement