Table 2.
Ca2+- and Sr2+-activation parameters in diaphragm fibers of the sheep during pre- and postnatal development.
| Prenatal |
Term 0 min (N = 5, n = 25) | Postnatal |
||||||
|---|---|---|---|---|---|---|---|---|
| 70 days GA (N = 3, n = 12) | 116 days GA (N = 2, n = 6) | 127 days GA (N = 5, n = 20) | 127 days GA (2.5 h MV; N = 3, n = 15) | 40 min (N = 5, n = 26) | +8 h (N = 2, n = 6) | Adult (N = 4, n = 16) | ||
| pCa10 | 6.93 ± 0.06 | 7.10 ± 0.03a | 6.67 ± 0.03ab | 6.80 ± 0.02c | 6.61 ± 0.01ab | 6.70 ± 0.02abd | 6.69 ± 0.04abd | 6.60 ± 0.10ab |
| pCa50 | 6.43 ± 0.05 | 6.67 ± 0.03a | 6.30 ± 0.02ab | 6.39 ± 0.0c | 6.40 ± 0.02abc | 6.48 ± 0.01bcd | 6.37 ± 0.14b | 6.41 ± 0.08b |
| pCa90 | 5.94 ± 0.09 | 6.24 ± 0.04a | 5.90 ± 0.02b | 6.00 ± 0.0c | 6.12 ± 0.02abc | 6.17 ± 0.02acd | 6.05 ± 0.02bcde | 6.20 ± 0.12cd |
| nCa | 1.94 ± 0.09 | 2.23 ± 0.11 | 2.55 ± 0.05ab | 2.38 ± 0.10 | 3.66 ± 0.15abc | 3.83 ± 0.12abc | 3.02 ± 0.27abe | 4.51 ± 0.88abcf |
| pSr501 | N/A | N/A | 5.36 ± 0.04 | 5.70 ± 0.06c | 5.64 ± 0.06c | 5.94 ± 0.02cd | 6.17 ± 0.01cd | 6.18 ± 0.06abcd |
| nSr1 | N/A | N/A | 1.57 ± 0.01 | 1.60 ± 0.08 | 1.78 ± 0.12c | 2.72 ± 0.14cd | 2.47 ± 0.39c | 4.85 ± 0.33cdef |
| pSr502 | N/A | N/A | 4.95 ± 0.03 | 4.94 ± 0.02 | 4.85 ± 0.05 | 4.91 ± 0.02 | 4.96 ± 0.05 | 4.88 ± 0.04 |
| nSr2 | N/A | N/A | 4.13 ± 0.40 | 4.10 ± 0.46 | 3.77 ± 0.36 | 3.02 ± 0.14cd | 2.77 ± 0.48c | 3.88 ± 0.52e |
| F1 (%) | N/A | N/A | 48.57 ± 7.69 | 47.32 ± 4.85 | 38.61 ± 2.32 | 40.36 ± 4.26 | 42.00 ± 5.00 | 44.30 ± 8.10 |
| SL (μm) | 2.19 ± 0.08 | 2.29 ± 0.03 | 2.28 ± 0.04 | 2.33 ± 0.05 | 2.42 ± 0.02abc | 2.49 ± 0.03abcd | 2.50 ± 0.04abcd | 2.64 ± 0.12abcde |
GA, days gestational age; MV, mechanical ventilation; N, number of animals; n, the number of fibers analyzed. Values presented are mean ± SEM. Superscript letter indicates significant differences (P < 0.05) between the following groups: asignificantly different from 70 days GA; b116 days GA; c127 days GA; d0 min of breathing at term; e40 min of breathing at term, f+8 h of spontaneous breathing after term birth. N/A = not applicable, as the force–pSr curve of fibers at 70 and 116 day GA were fitted by a single exponential function. pCax = indicates the amount of Ca2+ needed to produce “x” amount of force; nCa = the maximum slope of the force–pCa curve. pSr501 = amount of Sr2+ needed to produce 50% of the force–pSr curve described by the first exponential. nSr1 = The maximum slope of the first exponential. F1 (%) = the proportion of the force–pSr curve described by the first exponential. SL, sarcomere length.