Table 1.

Guanylyl cyclase versus guanylate kinase activities in mouse retinal tissue

Tissue	Enzymatic activity
	RetGC (nmol cGMP/min/retina, mean ± SD):
WT (Rd3+/+) retinaa	0.9 ± 0.2, n = 20
rd3/rd3 (Rd3-/-) retinaa,b	0.06 ± 0.02, n = 9 (p < 0.0001)
	GMP phosphorylation (nmol GMP/min/retina, mean ± SD):
WT (Rd3+/+), whole retina	31.8 ± 0.15, n = 5
Rd3+/+, inner retina	10 ± 0.91, n = 5 (p < 0.0001)
WT, photoreceptor layerc	21.9 ± 1.74, n = 5
rd3/rd3 (Rd3-/-), whole retina	28.4 ± 4, n = 5 (p = 0.11)
rd3/rd3 (Rd3-/-), inner retina	10.2 ± 1.25 (p < 0.0001)
rd3/rd3, photoreceptor layer, not corrected for degenerationc	18.14 ± 4.18, n = 5 (p = 0.37)
rd3/rd3, photoreceptor layer, corrected for reduction of photoreceptor countb,d	24.9 ± 5.72 (p = 0.52)
rd3/rd3, whole retina, corrected for reduction of photoreceptor countb,d	35.1 ± 4.36 (p = 0.336)
	(GMP phosphorylation rate)/(RetGC rate)e
WT, whole retina	35.4 ± 8
WT, photoreceptor layer	24.3 ± 6
rd3/rd3, whole retina, not corrected for degeneration	473 ± 171 (p = 0.0046)
rd3/rd3, photoreceptor layer, not corrected for degeneration	302 ± 122 (p = 0.007)
rd3/rd3, photoreceptor layer, corrected for degeneration	415 ± 168 (p = 0.0065)
rd3/rd3, whole retina, corrected for degeneration	585 ± 208 (p = 0.0041)

RetGC, retinal membrane guanylyl cyclase.

Mouse retinas were extracted at 3.5 weeks of age and assayed as described in Figure 4. RetGC and guanylate kinase activities were assayed as described in Experimental procedures; p—statistical significance of the differences from the WT from ANOVA/Tukey’s HSD post hoc, unless indicated otherwise.

^aThe entire RetGC activity is present in photoreceptor layer and is undetectable in the inner retina (27, 38).

^bCorrected for ∼28% reduction in photoreceptor count.

^cThe activity in the inner retina subtracted from the activity in whole retina of the respective genotype; (μ₁ − μ₂) ± $\sqrt{\text{σ}{1}^2+\text{σ}{2^2}^{}}$, where μ₁ and μ₂ are average activities in whole retina and the inner retina, and σ1 and σ2–their respective standard deviations. Propagation of error algorithms hereafter are from an open-access on-line resource Chemistry LibreTexts, https://chem.libretexts.org/@go/page/353

^dThe activity in photoreceptors plus in the inner retina; (μ₁ + μ₂) ± $\sqrt{\text{σ}{1}^2+\text{σ}{2^2}^{}}$; where μ₁ the activity in rd3 photoreceptors, μ₂ is the average activity in the Rd3^+/+ inner retina (aged line 362) or Rd3^-/- inner retina (aged rd3/rd3 mice), σ1 and σ2–their respective standard deviations.

^eMean average (μ) = μ_ph/μ_GC; SD = $\text{μ }\times \sqrt{{({\sigma }_{\text{ph}}/{\mu }_{\text{ph}})}^2+{({\sigma }_{\text{GC}}/{\mu }_{\text{GC}})}^2}$; where μ_ph is the rate of GMP phosphorylation, μ_GC is the rate of GTP depletion via RetGC, and σ_ph and σ_GC–the respective standard deviations; the p-values are from Student’s t test.