Carbonic anhydrase IV and XIV knockout mice: Roles of the respective carbonic anhydrases in buffering the extracellular space in brain

Abstract

Previous studies have implicated extracellular carbonic anhydrases (CAs) in buffering the alkaline pH shifts that accompany neuronal activity in the rat and mouse hippocampus. CAs IV and XIV both have been proposed to mediate this extracellular buffering. To examine the relative importance of these two isozymes in this and other physiological functions attributed to extracellular CAs, we produced CA IV and CA XIV knockout (KO) mice by targeted mutagenesis and the doubly deficient CA IV͞XIV KO mice by intercrossing the individual null mice. Although CA IV and CA XIV null mice both are viable, the CA IV nulls are produced in smaller numbers than predicted, indicating either fetal or postnatal losses, which preferentially affect females. CA IV͞XIV double KO mice are also produced in fewer numbers than predicted and are smaller than WT mice, and many females die prematurely before and after weaning. Electrophysiological studies on hippocampal slices on these KO mice showed that either CA can mediate buffering after synaptic transmission in hippocampal slices in the absence of the other, but that eliminating both is nearly as effective as the CA inhibitor, benzolamide, in blocking the buffering seen in the WT mice. Thus, both CA IV and CA XIV contribute to extracellular buffering in the central nervous system, although CA IV appears to be more important in the hippocampus. These individual and double KO mice should be valuable tools in clarifying the relative contributions of each CA to other physiological functions where extracellular CAs have been implicated. interstitial pH ͉ mouse hippocampus ͉ targeted mutagenesis

Carbonic Anhydrase IV Deficiency Causes Intrauterine Embryonic Loss in Mice

“…Interestingly, more CAIV-deficient male than female pups were born. This is in accordance with findings by Shah and coworkers [26], who, however, did not investigate the period during which the predominantly female embryos are lost. We here show that there is no misbalance in sex distribution during fertilization, early embryo development, and embryo implantation, but the observed misbalance in sex distribution is due to a higher death rate of female embryos during placentation Fig.…”

Carbonic Anhydrase IV Deficiency Causes Intrauterine Embryonic Loss in Mice

“…Interestingly, more CAIV-deficient male than female pups were born. This is in accordance with findings by Shah and coworkers [26], who, however, did not investigate the period during which the predominantly female embryos are lost. We here show that there is no misbalance in sex distribution during fertilization, early embryo development, and embryo implantation, but the observed misbalance in sex distribution is due to a higher death rate of female embryos during placentation Fig.…”

Carbonic Anhydrase IV Is Expressed on IL-5–Activated Murine Eosinophils

“…Notably, the human asthmatic airway is an acidic microenvironment (28); therefore, infiltrating leukocytes could potentially modulate the local pH if they expressed surface CAR. While we did not observe a difference in cellular and intracellular buffering capacity (11, 12) in vitro , we did demonstrate the pH buffering capacity of eosinophils, consistent with prior findings (29). CAR4 buffering is also accompanied by a readily detectable intracellular activity (30).…”

NMDA Receptor-Dependent Afterdepolarizations Are Curtailed by Carbonic Anhydrase 14: Regulation of a Short-Term Postsynaptic Potentiation

“…As shown in Figure 6C, there was no significant difference between WT and KO at any of the three time points (p > 0.2 for all; n = 12 slices WT, 14 slices KO). Thus, within the extracellular volume sampled by a concentric pH electrode, absence of Car14 had no significant effect on the alkaline transient, as reported previously when antidromic PATs were measured in the CA1 cell body layer (Shah et al, 2005). …”

Carbonic Anhydrase IV Deficiency Causes Intrauterine Embryonic Loss in Mice

“…Interestingly, more CAIV-deficient male than female pups were born. This is in accordance with findings by Shah and coworkers [26], who, however, did not investigate the period during which the predominantly female embryos are lost. We here show that there is no misbalance in sex distribution during fertilization, early embryo development, and embryo implantation, but the observed misbalance in sex distribution is due to a higher death rate of female embryos during placentation Fig.…”

Carbonic Anhydrase IV Is Expressed on IL-5–Activated Murine Eosinophils

“…Notably, the human asthmatic airway is an acidic microenvironment (28); therefore, infiltrating leukocytes could potentially modulate the local pH if they expressed surface CAR. While we did not observe a difference in cellular and intracellular buffering capacity (11, 12) in vitro , we did demonstrate the pH buffering capacity of eosinophils, consistent with prior findings (29). CAR4 buffering is also accompanied by a readily detectable intracellular activity (30).…”

NMDA Receptor-Dependent Afterdepolarizations Are Curtailed by Carbonic Anhydrase 14: Regulation of a Short-Term Postsynaptic Potentiation

“…As shown in Figure 6C, there was no significant difference between WT and KO at any of the three time points (p > 0.2 for all; n = 12 slices WT, 14 slices KO). Thus, within the extracellular volume sampled by a concentric pH electrode, absence of Car14 had no significant effect on the alkaline transient, as reported previously when antidromic PATs were measured in the CA1 cell body layer (Shah et al, 2005). …”

Carbonic Anhydrase IV Deficiency Causes Intrauterine Embryonic Loss in Mice

“…Interestingly, more CAIV-deficient male than female pups were born. This is in accordance with findings by Shah and coworkers [26], who, however, did not investigate the period during which the predominantly female embryos are lost. We here show that there is no misbalance in sex distribution during fertilization, early embryo development, and embryo implantation, but the observed misbalance in sex distribution is due to a higher death rate of female embryos during placentation Fig.…”

Carbonic Anhydrase IV Is Expressed on IL-5–Activated Murine Eosinophils

“…Notably, the human asthmatic airway is an acidic microenvironment (28); therefore, infiltrating leukocytes could potentially modulate the local pH if they expressed surface CAR. While we did not observe a difference in cellular and intracellular buffering capacity (11, 12) in vitro , we did demonstrate the pH buffering capacity of eosinophils, consistent with prior findings (29). CAR4 buffering is also accompanied by a readily detectable intracellular activity (30).…”

NMDA Receptor-Dependent Afterdepolarizations Are Curtailed by Carbonic Anhydrase 14: Regulation of a Short-Term Postsynaptic Potentiation

“…As shown in Figure 6C, there was no significant difference between WT and KO at any of the three time points (p > 0.2 for all; n = 12 slices WT, 14 slices KO). Thus, within the extracellular volume sampled by a concentric pH electrode, absence of Car14 had no significant effect on the alkaline transient, as reported previously when antidromic PATs were measured in the CA1 cell body layer (Shah et al, 2005). …”